A small note of caution.

A lot of the nicest American guns hover dangerously around the U.K. power limits. (One reason the U.K. rifle limit was set, at the urging of the U.K. makers, was to prevent their import and sale, at a time when Webley MkIIIs and BSA Airsporters typically made 9-11 ft-lbs.)

As you can see above, 45’s T&C made 12.45 ft-lbs.

As do many of the older Crosmans and Benjis. Especially in .22” - the .177”s are more likely to top out around 10-11.

Unmodified Sheridan C9s in good condition always break the limit, typically making 13 or 14 ft-lbs.

Even the cheapy Crosman 2200s can slightly exceed 12. Not always, but sometimes.

Pistols can be tricky too. For example I’ve seen a US test of a Crosman 150 CO2 pistol (the better-made grandfather of the 2240) that produced around 5.7 with Premiers. That’s a bit close for comfort if a forensic tester tried a more efficient (slightly heavier, better fit to barrel?) pellet in a centrally-heated lab.

There are of course loads of US air guns that will always be safely legal to import. Sadly, some of the best ones, in US form (not those modified for the U.K. market) are either consistently over our limit or sometimes over.