We have used a company called CTS near Liverpool for testing in the past, and I think they still do it - will try to find details. I have also heard that a shop in Tonbridge (Dive machine)
http://www.divemachine.com/ can test bottles, but send them out to a place near Southampton to be done.
I think bottles that fail test can be rendered scrap in several ways - including cutting drilling holes or crushing. Most dive shops can sort testing of fill rigs but not many can test wrapped tanks.
Is that confirmed that HPAC no longer do testing?