Been there for a full once as I was passing, was ok. But Dorset dive are always straight. I've had one bottle bounced in 10 years which was sold to me second hand and disguised to look good. They told me exactly why it would fail. But several other bottles have been fine through test there and unless you've got something you can see on the exterior it's highly unlikely you'll fail a first 5 year test. From memory it's around £50 for one. I had one done there last year.