I had a similar dilemma and in the end tried shooting in my loft which is boarded. As long as you have a quiet backstop there's little noise heard downstairs even from an LP10. It also can't be heard outside. The house is detached so I don't know if it would be heard by neighbors however.

As for pistols I would stick with the FWB80 as its quiet and very accurate. An SSP shouldn't be any louder however and some models may even be quieter including possibly the FAS 604/6004. I have a Daisy 747 SSP which is the quietest airgun I've ever used and it's very accurate with a good trigger. Unfortunately it's also a heavy, ill balanced, low powered lump of die cast metal and plastic. I'm not a fan as you can tell!