I can only add... you haven't said what kind of subfloor or walls you have. If the floor is in good shape you'll still need a water resistant subfloor material. Here in the U.S. we use a product called Hardibacker, but many tilers prefer the common cement board. It can be applied in 1/4 inch or 1/2 inch thickness. If you intend to tile around the shower/tub, you'll at least need greenboard for waterproofing, although I would recommend the cement board as well...
Additionally, you may need an extra thick wax ring to properly seat the toilet when you're ready to reinstall it...
I just finished a 6 X 12 foot bath with tile as you describe. I opted for 12 inch tile rather than the smaller tiles to make for fewer cuts...