if you get a leak they are easy to fix, barrel cleaning is the same as all other rifles, if you use dirty pellets it could foul up so it would hurt to clean it from time to time, but after a clean bear in mind you will need to "condition" the barrel with a few pellets before it will group like a lazer again.
I got a new one about 6 weeks ago and it wouldnt group very well at 30yrds with .177 jsb 8.44 so I swapped out the valve housing as I heard that the spring could bind up. that solved the grouping and I was able to get it up to 11.4FPE (from 10.2)
Then it dumped all of its air - turned out the valve "Delrin" seat wasnt delrin - is a hard rubber oring, mine came off so the brass collar was loose. I swapped it for a standard valve pin and its worked perfectly since,
So the UK versions as standard leave a little to be desired, but are easily fixed
Mind you not as bad as my wildcat - when I got that it maxxed out on hammer pos 7 at 8FPE, this has been fettled and tweaked and is on 11.7 with jsb 18g. and is super consistent.
I wouldn't want anyone messing about with my FX's -so if you have any issues let me know.
My main point here is that as the FX's are so well designed and made - they are a delight to work on