I do it myself, have done for years. Get a workshop manual and study it before attempting the job. Although I've never had to resort to this myself, with digital cameras, it's easy to take photos of each step you take dismantling the bike, and then view them in reverse order to put the thing back together if you fear getting lost. Use ziplock bags to keep the bolts and screws in. I use a different bag for each section of the bike, if the job is a big one. You do need the right tools, buying a decent spanner, socket, and allen key set shouldn't cost you a fortune. My advice though, is to get a good ratchet and excellent screwdrivers. The cheap ones that normally come in a set are crap and you'll do a lot of damage if they slip. My main advice is to be patient and don't try to rush the job, set aside a whole Sunday for instance. A few bottles of beer, a couple of mates and some tunes blasting in the background all make for a good day. Also find a forum for your bike. You'll get lots of help and advice. Buy parts online and you'll save money too.
I'm not sure how the laws work in the UK, but here in Australia, you do not need to take your bike to get serviced by the dealership to keep your warranty in check. Any licensed mechanic will do. Many dealers here imply that warranties will be void, but it's illegal for them to do this. When I owned a service station it was sweet as I'd stamp the log book with my own stamps. When I took my old GSXR1100 to get a starter motor oil seal replaced under warranty, the manager tried to pull a swift one on me, but I told him that if he didn't replace it, I'd call the department of fair trading and he quickly changed his tune.
When I bought my CBR1100XX, I was appalled at the shoddy work of the dealers. The sump plug was loose, the radiator hose was loose and the tyres were 10 psi off the recommended pressure straight out of the crate. I took the bike to a local father & son shop who did the mandated servicing for the first two years, after that I did it on my own.