Some of the stuff is fine. BUT, to date I can safely say to avoid:
The ?11 springs, they cannot prop the vehicle up level
ANY V8 ignition components, rotor arms, dizzy caps, leads the lot. Lesson learned, they MUST be LR gen for a V8 to run properly.
Accelerator cable which spilt the wire from the fork 3 times
Numerous problems with Series brake slave cylinders, they leak and fail almost instantly when fitted and are a serious safety issue. The threads for the pipe unions are also known to be badly made and leak.
There are more, but my rule of thumb is to only buy britpart when it is not safety critical or necessary for the correct function of the day to day running. I buy very few parts from them nowadays.