Uniform (including various sports'kit) always works out expensive (as mentioned already on thread) mainly because you have to buy from the school shop as opposed to mothercare/tescos/asda/sainsbury's etc etc. but I think most school shops have what they refer to as 'nearly new" (so 2nd hand !) clothes that you can buy - mine are happy to do that at the moment.
School lunches are included in our fees, as are the majority of after school activities.
We have to pay extra for some after school activities, but only those where expert tuition is needed so eg horse-riding, mountaineering, karate, etc etc. Included in fees are various during and after school activites such as dance, football, rugby, tennis, swimming, basketball and the usual "mainstream" sports such as hockey, netball, rounders, & cricket. I guess, if you worked it out you'd be looking to budget an extra 20% of the annual fee for 'extras" but that would depend on what DC chose as activities.
EYT - best decision we've ever made tbh, particularly when what would have been our DS's senior school was featured on national news recently with 'vistors' to the school carrying out a violent hammer assault on one of the pupils.........