I also dont want to charge stupid amounts and do myself out of future work because its very high profile. .
Number of staff: 7,085
Total spent on wages: £115,873,000.00
Average staff pay: £16,354.69
So don't feel obliged to work for free 7,085 people certainly don't!
A strange but true story is that I know the person who shoots cheque presentations to the YMCA, these cheques usually amount to a few hundred pounds, the YMCA pays him £125 to take photos of the presentation!!!
(The charity isn't Barnados or YMCA )
Finally, a thought, if you charged them the correct rate for the job, you could then donate the money back to them and claim "gift aid" thus they would benefit from the tax in addition.