Housemate/her boyfriend are ALWAYS in the bathroom

How long is left on the lease?

Honestly OP I’d style it out until the lease is up. Get some ear plugs. Maybe ask for a few quid from the BF to cover the costs. Then maybe move in with the bf or your own place.

Whoever you live with they’re gna piss you off. It’s part of sharing. So you live alone and pay the price or you have to compromise.

I think you might be fixating on this a bit- who counts the number of times the tap is turned off and on?

Childish opening line - don't ever start a serious conversation with "hahahahaha" as nobody will ever take you seriously.

Also 4 nights a week is a lot for your boyfriend to stay. It's not 6/7 nights per week, but it's splitting hairs to say he never showers there. You probably need to either accept that both of you benefit from your boyfriends being there a lot of the time, or move out. Your issue is clearly that you think they have no social life and are irritated by the fact that they're constantly in the house - if your housemate annoys you, that's fine. And valid. But don't make it her issue. It's double standards trying to blame the fact that he "doesn't pay" when in reality the issue is that they just get on your nerves.

Could you rent with your boyfriend?

@MelonHead2 as a grumpy 48 year old who used to be super apologetic people pleaser I used to write letters like that. I don’t anymore. Take out the lols and hand wringing statements as people have suggested. Others have given good advice so I won’t add more other than we can be assertive and still nice without having all the ‘if you dont mind? Could you possibly.., I don’t want to be a bother…’ these put us in a position of weakness and on the back foot immediately.

Blackout sleep mask & white noise.

My god OP grow a backbone.
You can't send a message as a doormat and not expect her to wipe her feet on you!

'Hi, I've noticed that your bf is here every night, I don't want to be paying half the bills as that's not fair when there is now a third person using utilities on a daily basis. I only live here 4 days and if my bf is here, he isn't allowed to use shower/bath utilities as I made it clear that we share the bills and it wouldn't be fair. Please let me know if you want to discuss.'

There is a difference between someone who is clearly a visitor and not using the facilities (eg the shower) vs someone who has moved in.

The bills should not be split 50/50 if bf is there full time.

Drip feed! So you also have a boyfriend. Double standards much?

If your BF is there a lot too, then you've not really got a leg to stand on.

I'd just message saying that you were really tired last night and her BF was quite noisy in the bathroom and for a long time. Going forward, can you all agree that the bathroom is off limits for showers/bathing when someone is in bed for the night or after say 10,30pm on a weeknight?

Don't start a request for money with an apology and a hahahaha.
If your boyfriend stays over four nights a week, I would leave it to be honest OP, you've got less of a leg to stand on by far. You both want to be able to have your boyfriends stay over, and you will absolutely be doing things that piss her off, in the same way as their bathroom use isn't regulation according to you.
It's part of sharing a house, and I think you need to suck it up and get an eye mask and some earplugs as I said before, if you ask her boyfriend to contribute, she will just ask you for a contribution from your boyfriend for the nights he spends there.

Try not to obsess about it, stick a podcast on and roll over.

No point in grumbling online if you are putting up with it in real life. I would never be subsidizing someone else's boyfriend or waiting for him in the bathroom on a regular basis. But it seems you have been fine with it so far and haven't said anything.

That's so frustrating. I need to pee a lot at night so even hearing water running would set me off. Maybe knock after about 5 mins and say you need to go? Then maybe it would give you an opening to talk to flatmate about the ongoing issues if you find confrontation difficult. He is there far too often for someone not paying his way, your bathroom needs are priority while he is not a tenant

He is staying at yours far too much.

You need a maximum number of nights (say 2) that he can stay at yours, otherwise he contributes to the rent and bills.

He is using electricity etc by staying and interrupting your sleep and making mornings difficult when you're getting ready for work. He's not a tenant, so he either needs to make his presence less-impactful or pay an equal share.

This totally reminded me of a housemate I used to have years ago. She was an early bird and took hours, literally hours to get ready in the morning. She would go to bed about 8pm every night (which was great, flat to myself!) but she woke up to start getting ready for work at 3am. She'd leave about 6:30am ish to get the train. But it was literally a 2 hour routine every morning, at least, in the bathroom. She'd wake me up showering at 3am every day. Some days I would be out with friends and not even get home until 3-4am and we'd bump into each other trying to use the bathroom in the middle of the night. More than once, I was clogging up the bathroom, er, with a guy I was dating, while she was waiting around to have a shower in the middle of the night. Awkward.

I think, yes, if boyfriend is staying over, he needs to be contributing or they need to share between their two places a bit more equally, which will free up the bathroom more for you.

A mix here.

You can certainly ask that they not play videos or music in the bathroom, since that carries through. But your complaints that they 'decide to use the bathroom at 11pm' or turn the taps on a few times and have the lights on there are not reasonable.

If you're awake, you might need to use the bathroom. This is true even in the night, but 11pm is a reasonable time to be up and need to get ready for bed. You can't expect anyone to use the bathroom in the dark just because the light shines into your room. (Your room and the bathroom have one of those windows in/above the door?) It's also normal for a washing routine to involve turning the taps on and off a few times. Turn it on to wet your toothbrush, turn it off not to waste the water, turn it on to rinse the toothbrush and your mouth. Then to turn it on to rinse your face and off to apply a cleanser, and on again to wash it off. You can't expect people not to use the bathroom in a normal way.

Talk to them. He has “moved in” and you are still paying 50% when you are sharing with two people. He needs to spend less time at the flat. 6 days a week is unfair. Maximum of 3.

Explain that whilst on your bedroom the bathroom light shines into your room (could you cover this up at all?) and that you can here him pottering around there. You’re not suggesting a “no bathroom after 11” rule but sitting in there watching videos is noisy.

Just tell them they’re disturbing you. I love a bedtime bath but wouldn’t want to bother anyone else.

How easy would it be to find somewhere else? I would speak to your landlord about the amount of time he’s staying over. It sounds as if he’s moved in by stealth. If they only stay at his for 1 night, is he living at home or something?

I'm amazed you haven't spoken up before

there needs to be a rota and tbh he needs to not be around so often, he basically lives there!

.... or he needs to split the bills and rent with you if he's basically moved in. Living with a couple isn't fun OP, I feel for you.

In this case then let her know this is unreasonable, he needs to be not there more than he is. If you're feeling resentful about the amount of time he spends in your home, than everything he does will piss you off, evening if the act itself isn't particularly unreasonable.