Following a conversation on Sunday morning I thought I would post this for those that don't know:
Boots the Chemist (other suppliers are available) do gel insoles that can be cut to fit and make your unforgiving fell shoes MUCH more comfortable.They do not reduce the volume of the shoe much and I have not had to modify my shoes in any way. I know BrianMC hasn't either. They really help protect your soles from those painful strikes onto sharp stones, especially if your wearing racing footwear like the innov8 mudclaw or x-talon. I thinkl they cost about £8.