Be honest… what sort of response do you think this prospective employer will give me?

Presumably you’ve got full time childcare for your daughter so what difference does it make to her?

This! It's only reading mumsnet that makes me realise how disadvantaged working mums are as a direct result of working mums. The entitled attitude is appalling. Thank god for EDI because if people weren't checking, I reckon an awful lot of employers would preference men.

Did you say you're working your notice from your job so now you'll be unemployed,?

Why did you apply, go for interview and then accept the job if you can't face the commute and the more demanding role?

Honestly, working FT is easier when DC are in nursery/ child minder. Once school starts, it's a different ball game....
So either start in September to get yourself settled or stay put in your current job.

I can't see any employer agreeing to a May start date unless you got the job because of some very unique skill set or nepotism.

I’d say no outright if you requested this and would be seriously annoyed that I’d even hired you in the first place as it’s a ridiculous request and shows a complete lack of judgement and self awareness. So no, if you actually intend to start rather than walk away assuming they say no, don’t even ask in the first place. And I think they meant two weeks or so re the time off in between not a month or more unless that was agreed upfront. Certainly not 6 months.

What was your reason for wanting to leave your current job? Have they already hired someone to fill your role?

Also, the suggestion of "taking some time off in between", I would interpret that to mean take some time off when you finish your current job before you start the new job aka have a holiday or have a break and be ready to start fresh! I think they would still be expecting you to start at the end of September, I don't think they intended for you to interpret it as "take a couple months to yourself, we'll wait".
They absolutely won't wait until May for you to start, and almost certainly won't wait until January either. Even suggesting it will make the runner up candidate very happy when they withdraw your offer and offer it to them instead

I think you should withdraw from the position and allow them to find someone who meets the terms they want. It doesn’t sound as though you’re the right person for the job.

What has the age of your child to do with it, unless you’re thinking that when she’s four, she may be able to entertain herself more, whilst you’re working. Are you hoping to persuade them about hybrid working too?

What you are feeling is entirely reasonable. My kids are much older and I feel exactly the same - it's about work life balance and for some people that's more valuable than the alternative role. I wouldn't however have accepted the offer (and have withdrawn from processes for that very reason), but you are where you are.

What will you do if they decline the change? Can you stay in your existing role?

I would probably ask for a gradual increase in office ours within your timeframe. I'd be really upfront and just say logistically and practically you are really struggling with the big jump, but really want it to work and think that would be the solution. I would though be fully prepared for them to turn you down, so that's the risk.

Are you looking after your daughter currently whilst working from home?

If that’s the case, why did you even apply for the job, or was it with the hope you could wfh some of it? It sounds like the recruitment process has been long enough that you’ve had plenty of time to consider this.

I can't imagine they'd be happy holding the role that long. If it's a needed role then they'll probably recruit elsewhere. Or if they can manage without for 8 months, they'll probably realise they can manage without it altogether.

Unless it's a tiny employer it's unlikely to be the first time they've encountered something like this ... all part of life's rich tapestry as they say

Shame, though, that folk don't always consider how it can reflect on all working mums - as if there aren't enough barriers already

I would say suck it up

Another point you need to consider is if this new role is in the same industry - people talk and if you mess them around you can be sure it will get mentioned at the next get together / industry event etc. Could you suggest that you start in September but do a phase into the office so you start at 3 days WFH 2 in the office then after 1 month move to 2 days WFH and 3 days in the office and then in the new year move to the 80 / 20 split. They might be amenable to that rather than a deferral until May. The current job market is really tough at the moment and I suspect they will be able to find another candidate who is willing to do it on the terms you were originally offered. It’s very much an employers market rather than employee and you knew what the terms were when you accepted the role.

Assuming your daughters in an 8-6 nursery, if you were considering starting a new office based job, id start it ASAP.

Having kids at school, I feel like I'm forever asking for time to get to the open afternoon, parent's evenings, the nativity, meet the teacher day, get the kids home and fed before the school disco etc etc.

In my experience, private/childcare nursery (as opposed to a termtime school nursery) is actually much more compatible with having a job than school is. It may be better to get the "I'm a reliable worker" credits built up for a year before your daughter starts school and you suddenly find yourself needing an additional day WFH to get to whichever school event is on that week.... (I reckon there's an average of one event per month for us that needs an adult to pop into school, though not evenly spread though the year. Plus school holiday juggling when the holiday clubs are even shorter than the school day...).

Sorry but my only thought here is ‘fucking hell’.

Also, September is hardly winter.

Can’t believe I was worried about asking my new employer if I could work 8-4 instead of 9-5.

Withdraw from the job or start when agreed. I really don’t understand why you think companies employ people they don’t need straight away?

What the hell?? Why did you even accept a job you don’t want? They obviously need a job filled and you’re definitely not it. Just withdraw and let them find someone who wants to y’know, do the job and set foot outside sometimes.

My response would amount to a politer version of 'Either shit or get off the pot'. You'd be massively taking the piss to ask to start EIGHT MONTHS later than you agreed.

Personally Id start the job, work around the issues for a few weeks and then have a conversation with your line manager. You may observe that one day very few people are in , or that the people who you need to interact with are not in. So you could ask if you could have flexibility on those days. Far easier to have the conversation once you have the lay of the land.
Having said that if you literally can't do 80pc at all then you need to withdraw. Will your current job keep you on?

I wouldn’t, you need to just get on with it, like if you asked me that I’d withdraw the offer. You agreed to this job and they hired you in good faith, no you’re wanting to change it!

your daughter will have to be in childcare at ages 3 or 4. What difference does a few months make ?

As the employer I'd be very pissed off and would look into rescinding the offer. Not just for the dithering but also because it's clear you don't want an office-based job and aren't going to be around long.

If you’re worried about weather then surely September is better than a January start? That’s only a couple of weeks away and September can still be pretty lovely. January is almost never lovely though - much more risk of snow, ice and a disrupted commute!

What childcare do you currently use? You don’t have your child there when you’re working do you?

I think they would say fuck me we’ve a right sort here!