Are we all done? ROFL
Look the kicker here is the OP simple didn't tell the test house what he had needing testing.
I quote "Tells me he wants double the test fee for 4 of them because they have a round base it will take a lot more labour"
Round base industrial cylinders are a menace the guy is lucky it got them done so cheap.
Each type of old round base ellipsodal, hemispherical to torispherical tells the test house how the cylinder was made also the manufacturer in most cases and what inspection tests need to be done prior to hydro.
Further the neck stampings tells the test house the type of cylinder they are dealing with.
His problem about the test house fitting new valves is also an indication that the test house is not sure if the previous valves were correct. If a standard stand up flat bottom cylinder to British standards or European turns us its easy and stamped around the neck is usually 25E that tells the test house the thread. Hence why I asked him these details.
Now with the old round bottom cylinders they can be 1" Briggs thread, or 25E or BSPT or even DIN 477
a heck of a lot more work to ring and plug gauge the lot. Any wonder it's cheaper to refit new valves.
not withstanding having to fork lift them around the place cos they don't stand up.
In a nut shell they cost more to test.
Now add the oddball NES (Navel Engineering Standard) cylinder that pop up from the mom and pop dive shops around the UK to cheapskate to buy proper cylinder they buy ex surplus and expect test houses to turn a blind eye and hydro a cylinder that is already older than its original design life.
Now for the benefit of you Yanks its like rolling up to you local test house with a bunch of ASME industrial cylinders and four ex DOT's where the SP permit has expired.
Better yet a ASME 8 Division 1 cylinder without the appendix 22
Its base type, thread type, manufacture coding, date of manufacture all have a bearing on the cost of retest. If you don't know this its not your problem, but you asked.