Shower valve leak

[Serval]

I've got a leaking shower mixer valve. That's got a small leak coming from the top tap handle.

Does anyone know firstly if this kind of thing is serviceable and how do the handles come off in order to remove the back plate in order to gain access? (There are no hidden grub screws or anything obvious as to how to remove the handles)
There are some stubby pegs that screw into the handles which I've already removed but the shortest one on the top of the middle handle seems to be fixed. can't see anything else that allows the handles to come off and I don't want to grip it so tight with a pair of pliers that I damage the chrome

I'm unsure of what brand this mixer is as there are no markings on it or no instructions from the previous owner.

If anyone has any ideas let me know.
Cheers

 

[Serval]

So I found a grub screw hidden under the pegs that stick out of the handles.
Fully loosened and the handles still won't come off