Attended the one day training course for the Operators Short Range Certificate (SRC) for VHF Marine Radio at the Port Edgar Sailing School. If you have read the RYA guides G22 and G26 beforehand then the course is a little slow but does give the opportunity to practice using DSC with a software simulator and you get to ask any questions you may have. The practical assessment is an area where most candidates (me included) seemed to stumble a little and need a few prompts but the written exam proved very straighforward.

You can find some free simulator software at YachtCom

GMDSS Digital Selective Calling Simulator DSC-D2