az91, you won't earn any thing like the majors flying the Caravan or King Air. I don't know their salary structures but I would be surprised if it was more than £20K to £35K as command.
These jobs definitely exist but they tend to operate out of smaller airfields. There is a operator of PC12s, callsign "mosquito" and they seem quite busy, especially in the Swiss Alps. It is interesting flying and you'll do a lot more "hands on tasks". As B2N2 alluded to, if you're after hours for that illusive command, you'll be waiting a while. Most average about 300 hours a year. Although, at the moment, the bizjet world is booming so the hours are there but nothing like a "low cost" airling.