Hi there I can't sleep it's the middle of the night and just sat here reading your post.. agree with all of the comments above. I was, like you, on my own from the start (6 weeks pregnant) - had help to move across the country when baby was 4 weeks, but that meant packing boxes in a 1-room flat in one place then living with those boxes... still living with some of them actually lol
Please don't compare your situation to mums you meet who have partners, or even mums/family who live nearby and come round to help.. because it's NOT the same.
The most important thing for you, is to focus on yourself and your baby. Your house won't fall down with a bit of dirt, but your child will grow so fast, before you know it they will be 1 and 2 and you will already be looking back saying wow, where did that time go. You can never go back.. so please enjoy every second of it. It's way more important to gaze at your baby, take a zillion photos, go for long walks, have as many cuddles as you can fit in a day..
"Lower your standards".. Yes! Take it from someone who used to iron bedding and towels pre-baby ha ha... I'll be honest and say that my (new) accommodation rarely got cleaned. The dishes could stack up for days until there was nothing left to eat from. The floor got hoovered once when my daughter was about 5 months, then at about maybe 9 months (I used to spread sarongs over the floor and she would roll around on those and they would get washed). Same with cleaning the bathroom... That's not very hygienic - it's only looking back that I can even see what a struggle it was - and I'm not advocating that level of uncleanliness.. but please don't beat yourself up about it.
In favour of the bit above about a slow cooker (if you have room in the kitchen). Ready Meals.. are better than whole packs of biscuits, and quicker/easier/less mess than preparing a slow cooker so can sometimes be the best option, and then just snack on fruit and keep hydrated if you're breastfeeding (I know couples where the guy later told me he used to bring his other half a glass of water any time she was breastfeeding.. it's those small things you aren't getting and don't even realise you aren't getting but you can keep a bottle of water around and look after yourself).. and things like just hoovering the bit of the floor you use most often isn't against the rules - because you get to make the rules :)
There will come a point as people have said above where you get a little, then a little more of a break between feeds and sleeping.. this totally depends on your child.. but it will get easier, later will come the point where they get introduced to cartoons and stare at Peppa Pig for a full half hour while you tidy around them :)
If people do come round - don't be afraid to ask them to help out, and especially if they make any mess.. I had one family member who brought her toddler round a few times, each time they made so much mess and then just left - it took me up to a week to tidy the room afterwards, which sounds crazy.. but I should have been more assertive at the time and just asked them to help tidy, restore the room before they left.
RE: Home Start, I had a very bad experience where the volunteer told me in increasingly forceful ways that she was going to take my baby out/away from the house, then did (overriding my express wishes) - and Homestart were really 'off' with me for calling to describe that and just withdrew their services.. I won't go into the whole story, and not saying all their volunteers are like that, can tell some people on here have had good experiences - but just that note of caution, you should be able to be very clear with them what you need and where your boundaries are, and have them respect that.
Really hope you can take a deep breath, relax, go for some long walks and enjoy your baby :) xx