a1ex2001 said:
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Comming into your part of the house with out consent/notice is almost certainly illegal, tell him to stop.
It is, and yet isn't, illegal.
A landlord certainly has right of access in emergencies, and also has right of access to check the condition of the property, or effect repairs.
BUT .... that latter point should be done by arrangement and with at least 24 hours notice.
But as with most things, there's a balance. You can't just put off a landlord's access for weeks, because it "isn't convenient". Similarly, he can't say "be there in 10 minutes".
But other than situations like these, the tenant has a contractual right to "quiet enjoyment". The landlord does NOT have the right to just walk in whenever he feels like it.
As for withholding rent, be aware that you are in breach of contract if you do this, and could well end up in small claims court. There are a lot of things tenants a liable for, and some that they aren't. It was said earlier that you (the tenant) isn't liable for wear and tear, and that is absolutely right. But you are liable for losses, and damage.
Because you are liable for losses and damage, it is essential to get a full inventory, check it out, agree it with the landlord and both keep a copy of said inventory signed by both of you. It is also essential to thoroughly check the property when moving in, and to report any damage, marks, etc.
Look at it this way. You WILL very likely be held liable for anything found when you move out, and saying "it was there when we moved in" won't wash. Anybody can, and usually does, say that. So check, and report things. If equipment doesn't work, report it. If there's damage to the decor, report it. If furniture is scratched or upholstery torn, report it, do it in writing, and get a signature. If you don't, don't be too surprised if you get a bill later on. Oh, and also be aware that, depending on the tenancy agreement, each of multiple tenants can be jointly liable with the others. So if one of you withholds (or just doesn't pay) the last month's rent, you may ALL be held liable for it.
Also, if you don't leave the property thoroughly cleaned, don't expect the landlord to come round with a mop himself. He's probably going to engage commercial cleaners, at commercial rates (plus VAT) and YOU will likely end up paying for it. It WILL amount to a couple of hundred pounds, possibly more. The property should be spotless when you move in (and if it isn't, don't moan about it months later, report it right there and then), and you will be expected to leave it in that same spotless condition, because that is what the next tenant will expect to find.