Just very quickly......Mental health issues dont prevent you from having/obtaining FAC or SGC I have both.
Makes it complicated, frustrating and time consuming but not impossible.
I have had 2 spells of being, as someone else said earlier in the thread 'nuts' the last spell lasted for 18 months during which I was very unwell.
I had to have several 'crisis' meetings with psychiatrists, GP etc and they all agreed that i was 'neither suicidal or homicidal'
I also have a couple of serious criminal convictions (20 years ago).
I actually feel the limit for airguns is about right and if you want more then get off your arse and apply.