And merged again
As ever (and it's been posted many times in this thread), you can claim whatever business expenses you incur provided they were wholly and completely for the purposes of running your business (that is, with no personal benefit at all). Obviously registering as a fish and chip shop wouldn't make a lot of sense, but we have various people here registered as models, entertainers, dancers and so on - back when I had an accountant, his regular suggestion was therapist. In other words, anything that's so vague it's open to pretty much whatever interpretation suits the situation.
Again, it doesn't matter what you buy - HMRC are interested in how much you've earned/spent. An example would be that if I was an artist who decided to use condoms to put over my paintbrushes and keep them clean, I would absolutely be claiming that as an expense.