I agree. Its actually very hard where I am to just get one filled.
The guy I'm reluctant to go to in yeovil is now charging £10 to refill a 3ltr bottle, I'd hate to imagine what he'd want to charge for a retest (if he would do it). It's only been filled 3 times, as I've always used a pump, but had the bottle as back up if I was either in a rush or feeling ill.