From memory i think they were nervous about carrying something "gun" like and also werent sure on the rules around high pressure containers. I should mention that it was the shop owner who suggested the postal route as the easiest. I let them off, i was young and they paid for it allUnless they bought a serious amount (or they were also coming back with their import limit) then the attempted smuggling caused customs to put on the charges
The circa £45 bill was part import vat and part courier fee (probably £8 to £20 fee) so £25 to £37 import vat
If they brought it back in person then there would have been no charge due to personal allowance or they would have only paid the import vat and not the courier fee ...... and the international postage when they sent it