OYSTERTEC

Teci,
If you are as you say reasonably competent at diy then doing the bathroom can be fun, rewarding and reasonably cheap!
Only advice I would give a first timer is to buy a handful of in-line ball valves (the type you turn on and off with a screwdriver) they cost a couple of quid each. Fit one of these at an easily accessible point on each of your incoming pipes. Then you can have the water on in the rest of the house whilst you work in the bathroom.
Fit a one every now and then as you progress round the room and that will section off manageable areas. By the way current regs means you should fit such valves on each feed pipe for every tap, very handy for maintenance on taps in future years without water drainage / wastage.
Good luck if you do decide to go ahead.