The informal economy (and I do not necessarily mean one where you pay no tax - but that would be included also) is quite a big one in Cornwall so if you are looking for work you need to be mixing with people and all sorts of bits and pieces will open up in craft shops, tourism, marquees, building, farming, the big tourist gardens etc. If you have any skills and you get to know people then things may come your way. My brother in law has done marquees and now has a zero hours contract as an hgv driver, but will turn his hand to anything. My parents in law on moving down to Cornwall both put their names down for jobs at Treliske hospital and 2 hours work twice a week became a full time van driving job around the Cornish countryside so my FIL was as happy as a pig in sh** and MIL likewise in children's unit.
Decide what you want to aim at and you can make it work.