I would just arrange to go and have a chat with old HMC (or do it over the phone if there isn't an office near you). Nothing much can go wrong. After all, you can earn something over £5000 before you pay any tax anyway, so you won't be stung for tax. My motto is to play as straight and honest as you can in these matters, unless you want to dodge and weave and are (or have) a very clever accountant.

Hi. I'm having trouble with a client who can't read my Word docs (created on Mac, but with suffix .doc which always work with everyone else, whether using pc or mac). He tells me he has had similar trouble with someone else. Could it be Gmail (the emailer he uses), so making us use googledocs to exchange documents? Anyone any ideas how to resolve this problem? First thing, I guess, is to try using a different email provider.

getting paid/copyright

A few thoughts.
First, the copyright always belongs to the creator unless or until given or sold.The media know that.
Second, you (we) need to agree terms in advance (or at least have a clear, demonstrable 'understanding').
Third, you could get into long, complicated and expensive argument over this if things weren't clear at the outset.
Fourth, perhaps better to lose the battle and win the war. Just take a hit on this one and make arrangements for any future relationship (with this or any other client). If they have used your work once, in the long run you will do better if you don't fall out over one photo.

Starting up

I would talk to the Inland Revenue: they used to have a starter pack for people setting up on their own. I know, because I helped write it a few years ago!

I would be surprised if you need to register for VAT. I understand that while anyone CAN register, you don't HAVE to unless your turnover is more than something like £80,000. And you have to register if it LOOKS as though your annual t/over is heading that way. But I've heard it's a hassle to do, lots more admin.

I simply keep detailed records of all income and expenses, and when it comes to tax, just follow the guides that come with the Self-assessment form. But perhaps I would be better off getting advice from an accountant, though never have.

Unpaid bills

1/ Send Terms and Conditions (use other people's as a model, to suit you) before starting work
2/ By law the creators of original material own copyright unless assigned (sold or given) to anyone else. I include in my Terms and Conditions a reference to the fact that I own the copyright until the client has paid fees due.

Design=Apple

If you're going into graphics you just HAVE to go Apple. No question. If in doubt just ask some design companies. Ditto, they'll tell you about software. My understanding is that InDesign has pretty much taken over from Quark.