Slipstream, I am quite sure that driving offences do not matter with regards to obtaining a CRB, plus you can use the same CRB for being a CI at an ATC Sqn and a CGI at a VGS.
However, if you were to join a VGS and tried to obtain a Service Driving Permit (basically a driving licence for the RAF Landies), you will have to inform them of driving offences. Quite how much this will affect the likelyhood of getting a permit- I do not know.