Hi Honey and welcome to SAAFE

There is a recent-ish thread
here about finding accountants; it does depend to some extent on your location, I suppose, but any accountant should really be able to help - our business is not a complicated one and whilst it does ideally help to have someone with industry knowledge (there are still plenty of people out there who think prostitution is illegal, for example), it's not crucial and provided you keep your records properly I can't imagine you having problems. Accountants (and doctors, solicitors etc etc) are providing a professional service, and it is not their place to judge you.
The Tax Relief Diary I can ony imagine is not available because Jolyen has retired, although this is just a guess. You can easily make a record book out of a basic notepad though - you really only need to keep track of what has come in and what has gone out (with receipts, bills and so on) and your accountant will do the rest. I have one spreadsheet on the computer for expenses and you don't need too many sections, provided you keep your household stuff separate from the rest (I have Hotel/Travel, Advertising/Promotion, Clothing, Phone/Internet and Sundries (condoms etc) as well as a Miscellaneous section for oddbods.
As far as clothing goes (or any other expenses), you can claim for any cost which has been incurred entirely in the course of running your business, so civvy clothes would normally be a no no (as it could be argued that they would be worn for personal use too). I did have to buy a smart outfit for a particular booking a couple of years ago because I didn't have anything suitable, and I did put that through - the main thing to remember with any expense you claim is that you need to be able to prove it - I kept the ticket from the event I was going to on this occasion and it was fine.
If you do need to ask questions, the HMRC people are very helpful in the meantime. Good luck!