[QUOTE=Tom Barr;15735]Getting them hydro tested should not run more than a few pounds]
Nothing in the UK costs a few pounds!
Seriously though l have only once tried to get an extinguisher refilled - about a year ago. This was in Somerset so along way from where i live now. I phoned up a few different fire extinguisher places and was given a story about new bits of EU legislation and how they couldn't actually fill them themselves and they would have to be sent to somewhere ect etc... I can't remember the exact prices i was quoted but it was a lot more than the £10 each or so that i ended up spending on ebay. I think part of the problem was that i wasn't actually near anywhere that could do the job themselves.
In the past i have looked on reef forums for sources of CO2 refills and fire extinguisher places were often suggested. While i never found anything directly relevant to where i live i did get the impression that some places were much more helpful and much cheaper then others. It will definitly be a great help if people can post any info they get about such places.