Was there anthing you were doing / switching at the time the static appeared?
I have no experience on XK8s but this can happen due to lack of earth on Teeves brakes on Xj40s and on Ford Transit brakes. It seems completely random from one vehicle to the (apparently identical) next.
Check you ariel connections have not come loose and that the outer braid of the co axial ariel cable is earthed. Otherwise its a case of going round everything with probes / crockodile clips.
Cheers