To check your gun at home, just use the air you have after you have played.
e.g. don't spend five minutes shooting bushes with your leftover paint at the end of the day and you will have the air to check for leaks and some test shots after cleaning up / servicing etc
If you don't have enough air after the last game, and the site have shut down the fill stations then consider a spare cylinder an investment (About £30 for a 3000psi and fill it sometime on site during the day)
A compressor that can run the required pressures will cost serious money
If you do need more air, and it is practical, then a scuba cylinder and fill rig will set you back a lot less then a compressor
Other obscure options are a 'shoe box' compressor - still costs a bit, is doubtful to be available in theUK without extra expense, and just gives extra pressure to an existing source. These will also take hours to fill. (They are designed for people in the middle of nowhere)
Or a stirrup pump - You would get a serious amount of exercise for not a lot of air