Hierachy, just leave them to get on with it, only take the weak ones out if they're not getting any food, like stubby said, it's just thier way of life.
£265 is not a lot of money for a new rifle, I doubt you would get anything to equal your 90, for that money, not new anyway, second hand you may pick up a bargain.
I have 12ltr bottle, don't ask how many fills I get from it, because when mates arive to go out for a twang, they always forget to fill their guns, you'll find this when you get your bottle, It's a bit like crashing the faggs.
Mate was in same positon as you, he has young kids, thought is was a cheaper way to go, shop say repair is down to him, even though he bought pump with rifle, thought he was going to pop the shop owner when he said he should have read the manual.
If you can run to the extra cash, then go for bottle, the air is dry in the bottle, pump draws in moist air, mate just sent his gun back because of moisture, knackerd his piston.
Kept my lurcher inside, and she used to go mental in snow, when I get her replacement, it will live in the house, if I had more than one, they would be kept outside.