why does it cost to re-test them ??? and where can you re-test them ???
Hpac will do the test for you, cost is 23.50 plus VAT (I think...) which is about 27.60 all together.
Test involved the bottle being pressurised beyond the normal working pressure (50% more, I think) and then they check to make sure the bottle has not been permentantly deformed by the pressure. This all takes place under water and its water that is pumped into the bottle too, hence HYDRO testing. So I hear.
EDIT: Don't try this at home kids.