I presume you're looking at day school fees, not boarding - so fees aren't quite as
as wishingforcrystalball's post.
In Bristol, most of the independent schools have similar fees at the moment - around £10,000 a year for secondary, £7,000 a year for primary - except for Badminton and Clifton College, which are at least £15,000 a year for day pupils, obviously much more for boarding.
Lunches cost £2-£3 a day. Some schools include all text books, stationery, compulsory trips etc in the fees, some charge extra.
Uniforms are variable - cheaper for boys, as they can usually wear standard grey trousers and white shirts, plus school blazer, sweater, tie etc, but the logo-ed items can often be picked up very cheap from the school second-hand shop. Girls often have to wear school-specific skirts, but again second-hand is cheap - until the school decides it's time to redesign the uniform, of course.
Sports kit can be expensive, as things get worn pretty hard and can't always be found second-hand. The list of rugby/hockey boots, mouth guards, shin-pads etc is pretty long - I reckon I have spent at least £200 per child on sports kit, but I buy big, so most things apart from shoes/boots should last more than one year.
There are often lots of expensive school holidays on offer at the secondary stage (as there are at many state schools) but you don't have to do them, apart perhaps from an annual PGL type trip during term time, at about £300.
Optional activities at school sometimes cost extra eg DS has done a term's worth of skating lessons, which I think cost about £60, but there are usually free options for the same time-slot.