I know. But sometimes on these threads we can make it seem this is a casual item or people can get that idea.
If they return the bottle it's out of test it involves the OP taking it away, which as I am lead to believe is against the transport regulations which is what the test is about.... you can fill HPA at home without a test, it's not illegal or anything. It's when you move them that matters. The cylinders have to be either in test to be moved, or destroyed. Like an MOT there's a certain set of regulations for testing, and on failure there's a certain set of regulations for when that happens.
The reason they have to be destroyed is so when they are scrapped someone doesn't need to inspect them to make sure they're safe for recycling, they are no longer cylinders, just 3 bits of cylinder.
The centre is a business. They get things in at X price, they do Y work and charge Z. I don't see why it should make a loss for it's time and expertise to give someone a £10 or so discount. They'd still have to charge VAT.
Now there's a really simple way of solving this, instead of wasting all this time on the internet someone could phone Idest and ask, or failing that 2-3 test centres and see what they say about giving a bottle back when it's failed. Once you have that info then you can move on. It would be interesting because I had a cylinder fail once and I didn't get to keep the head... but then I'm not that tempted to do a diy assembly after buying a cylinder and I suspect the for the costs involved it wouldn't have been much of a saving.
When I take my bottles in, I trust the guys who do the work because they're the qualified ones and they don't want to upset me because I then keep going back for air... I know it's upsetting, I've had 2 fail, one never been mistreated and was just 10 years old, but it happens and that's why there is a test for all these bits because it does happen.