Here is the reply from CAMC Tech Support received today. As you can read, their current thinking is that the situation is a bit of a mess and need clarifying.
"Following on from the conversation you had with Kelly earlier today, we
have just gotten a response from our technical manager, please see his
response below:
To the best of my knowledge, there is still no in-situ inspection service
for fixed tanks available in the UK. Gaslow used to offer an exchange
service for their refillable cylinders, but now state on their website FAQs
that recertification is more expensive that replacement with a new
cylinder. Alugas in Germany will recertify their refillable cylinder, which
some owners have used with positive feedback. Details here:
https://alugas.de/en/index.html You can book an appointment with them a
few weeks in advance of travelling.
This issue has been flagged up by ourselves with the National Caravan
Council. We were told by them some time ago that an inspection service
would launch shortly, but that has not yet occurred, as far as I know. Yes,
it's quite a problem, but one which is beyond the Club's capacity to
resolve ourselves."