Om the UK registry, the MMSI belongs to the
boat, not the owner.
Presumably Yacht Sandpiper is on one of the UK registries - part 1 or SSR. You will get
ownership transferred to you and you will keep the MMSI.
This is done because MMSIs may not be user reprogrammable in the
hardware - this is certainly the case with
AIS, can't remember about
DSC VHF.
Presumably MMSI "B" is the correct one, and it's this you'll use for
registration of the
AIS. But transfer the
registration of the yacht first, so you have the ship's registration papers saying this is the right MMSI. (Actually, I think the MMSI might be registered through
Ofcom.)
The old biddies at the MCA in Cardiff are quite friendly and helpful - you can
phone them up.
The
VHF will need to be reprogrammed to the correct MMSI - contact the manufacturer if the manual doesn't tell you how. I think some agents charge £50 for this.
You don't get to pick your own MMSI, so bringing the VHFs' MMSI with you isn't an option.
IMO part 1 registry is preferable to SSR if it has lapsed, but it requires a "survey".
If you're in the UK you will probably find the YBW
forums more helpful - no disrespect to this forum, just that most folks here are familiar with N American paperwork, and most folks there are British.