Tango Oscar,
I am not sure that is the case. Every club I have rented from (which is quite a few!) and filled up tax free has refunded the fuel at there own pump rate. The few times I have been via Lyd in rented aircraft rather than my own I have paid tax free but been refunded club pump price.
I also travel to Guernsey in the twin on a regular basis and we fill up there tax free and always get refunded at local pump prices. Makes a lot more sense than the time waiting for C&E to process the paperwork and cough up the lolly!