Seems like you haven't got much choices mate.http://uk.pcpartpicker.com/part/amd-cpu-fd6350frhkbox
Your motherboard at its best supports AM3+ socket CPUs (AMD FX and Phenom II Series).
FX 6350 is strongest CPU available for £100 which is compatible with your system. But don't worry, that CPU is strong enough to run all modern games with ease. One of the highly successful CPUs of 2013 and is quite capable.
Definitely the good and "only" choice for that budget.