Another vote here for the DVR2. I have one in my Wm20 and several other BSAs including the three wheeler.
I have been using them without any problem for years and Mike, who developed them, is as Ron says, a decent guy to deal with.

They are indeed on holiday ! On a boat somewhere with limited internet access. I had a short message back from them today. Hopefully we can get the reg in time for the near 2000 mile journey in September. I think I'm going to get a DVR2 for my G3l during its autumn rebuild too.