Would my house rules be unreasonable? #1 would be No Male Visitors overnight

Depends on if the OP is a Tennant of the flat or the homeowner

if she is a Tennant your correct
if she is the homeowner your wrong

Wow. What a response.

I think its very sensible. My friend let a room to a woman and before she knew it she was practically house sharing with a couple because the guy spent more time at her place than his own. Completely altered the way she could live within her home as there was this man there, in the kitchen, using the bathroom, and she ended up feeling like a third wheel in her own house. It was really difficult to row back from given she'd allowed the initial overnights.

This is nonsense. It sounds very much like you've never been or dealt with or even talked to someone who's been a lodger.
I've had lodgers for years, and those who've got to the point of coming round to see the place and meet me and DP have always been very proactive about discussing things like arrangements for visitors, boy- and girlfriends, how much they use the shared space and what the expectation is around socialising etc.

And the upcoming changes in the law apply only to tenants, not lodgers.

Isn’t that for shared flats though, rather than lodgers? The latter are covered by different rules

I'm not pedantic, I'm trying to understand how to read your comment as written.
OP has had a flatmate for a decade so clearly it's not a given that she's unsuited to having a flatmate.

You then clarified that the fact you wrote "I don't think you sound like a good candidate to have a flatmate" meant that you agreed that although you disliked the rules, other people would find them suitable.

I'm not bothering any more as you can't seem to make up your mind!

I’m afraid OP this won’t stand up in practice. You’re their flatmate not their mum, it’s a business transaction.

meaning even if they agree to it, if they break the “rule” you’ve got basically no power or way of enforcing it. Bar evicting them - but upcoming changes in the law mean that you will need a better reason than that.

Is it the man thing that you don't want? If your new flatmate was lesbian, would you be happy with her bringing women or a girlfriend over to sleep?
The OP has addressed that, more than once.

My and DP's relationship with our lodger is along the lines of enjoying her company from time to time; but she has her own life and is fairly often out early and back late, and in her room working/on the phone etc.
We wouldn't ever order her to stay out of the kitchen/living room, don't impose rules like set times for cooking or showering (in fact she asked whether we wanted to set the latter time, but we aren't that bothered), and are not 'a nightmare to deal with'

Irrelevant to the OP's question.
Also, people are different. The OP says she likes the company. Friends of mine with lodgers say the same thing. DP and I like it too.

No, I meant exactly what I said.

I think people like OP, who have all these rules and stipulations in a place that is supposed to be someone else’s home, usually end up being a nightmare to deal with. OP stated she might enjoy the company of a female flatmate from time to time, however they must have their own lives - insinuating that she wouldn’t appreciate them being home all the time.

Are you always so pedantic? Perhaps you would be the ideal flatmate for OP.

I couldn't think of anything worse at 55 than having a flatmate.

So did you mean to say "I don't think you sound like a good candidate for me to have as a flatmate", rather than OP being incompatible with any flatmate?

There is no harm in trying for what you want- some people would be fine with it. I didn't have this condition when I advertised for a lodger but she stayed with me for three years in her late twenties and never once brought a guy home overnight- and this was her choice. Some people are asexual, some women date women, she just didn't seem interested in dating. When I advertised for a lodger I thought house sharing with someone with a baby would be a deal breaker but I had interest- possibly because I was willing to accept lodgers with pets which I understand can be tricky to find.

Is this your own flat and a lodger coming in or a 50/50 flatshare?

Either way, I think it's completely reasonable to be specific about not wanting men to stay over if it's what makes you feel safe and comfortable in your home.

My mate has had lodgers who only stay in her flat during the week because she lives in a city and they're people who need to be there for a job or training but have a home elsewhere. This meant she could have visitors on weekends (e.g. me, I'd stay in her room not the lodger's!) or bring dates back. Takes a bit longer to find someone right but it's worth it to fit her needs. She priced it so it was cheaper than a full time let so it was an attractive option and the people she had were great, they were out working or training in the day and had low key evenings of coursework, gym or telly and food. It can work.

Is it the man thing that you don't want? If your new flatmate was lesbian, would you be happy with her bringing women or a girlfriend over to sleep?

Yes, I didn’t know about it and I think she realised from my face when she had been in my bedroom to put new flowers, etc. I wasn’t mad, I was just surprised because I didn’t know it was allowed.

Like I said I only went along with it because it was much cheaper than other places on spareroom (should have been my first clue), but unless you’re looking to save as much as possible, it’s an uncomfortable arrangement. Any friends and family could only come visit me for a day trip as no one could stay, it was a bit of a faff.

Absolutely.

Hence why my response started with the key word “I.”

🙂

OP I live beside a hospital and occasionally had student nurses/midwives stay short term either 4, 6 or 12 weeks when they're on placement and only stay a few nights per week.

There's also a shortage of accommodation for doctors on rotation who may need accommodation for 3, 6 or 12 months so someone like that might be a good option for you too.

Exactly that. Many might not apply but the ad might stand out to someone who wants that lifestyle.

Don't be silly. In a lodger situation it's perfectly normal to have rules like no overnight guests. And most mature people wouldn't expect to be able to have loud parties, or even want them.
All the lodgers I've had, and everyone I've met with a view to renting my spare room, have proactively brought up rules about noise/guests etc, and have been very respectful of the fact that it's my home. Yes, they pay to live there, but not as much as they'd pay renting in a houseshare or living alone. Anyone sensible realises that conditions will come along with the cheaper rent.

DH is looking for a 2 sometimes 3 night a week place in the White City area.
I would be very agreeable to him not being allowed over night guests or throwing parties.
He would like a shelf to keep tea, a mug and a box of cereal.
He has a good standard of DIY in plumbing, electrics and carpentry but will be off doing his best academic stuff during the day time.

The last place was dreadful. The remote landlord had a complicated arrangement which only became clear once signed up. Basically three different part timers using the bed on different nights. And it was expensive and not remotely a hotel standard.

I don’t think you sound like a good candidate to have a flatmate.

Seeing as she's had one for a decade that doesn't sound true to me.

I'm in my early 40s and I'd be fine with this. I'd be your flatmate lol.

People keep asking about female guests - OP has addressed this if you read her posts.