I think you'll be looked upon badly if you include clothes as a business tax expense and it may mean you get investigated a little bit more.
You can claim against utility bills but only for your 'office room', ie. 3 rooms, you need to divide the bills by 3 for instance. It's quite complicated for very little gain imo.
Definitely include the big stuff, furniture, PC, laptops, domains, hosting, advertising. They don't mind you writing this stuff off as an expense, but go overboard and they will look into your business and start picking holes.
Meetings/business lunches... sure. Keep the receipts and I'd probably make sure it's not Mcdonalds or a Kebab shop you're taking your clients/whatever to every Friday night
