Mark, out of interest, whereabouts is the dive shop you use.....we use one in Croxley green (nr. Watford) and they're always pretty good.
I gues your right though, prolly does depend on their insurance policy, as they might have penalties if caught filling out of test tanks or something like....
oh yeah, good point about checking what they fill too, we were lucky in that the shop we use (which happens to nearest) fill to 300 bar, anyone considering getting one should check weather or not their "local" dive shop has a 300bar compressor.
Mark, good thinking batman!