Register on the Guardian Home Exchange website. £35 for the year. You can then post details of your place, search potential swaps and make offers. It covers everywhere – a lot of ex-pats use it to arrange cheap trips back home to visit family etc.
http://www.guardianhomeexchange.co.uk/
Not done an overseas swap yet but we exchanged our 3 bed semi on Dartmoor with a family in London for their huge Edwardian town house in leafy North London over half term. Saved us £££s on accommodation and worked out really well for both parties.
We’ve already had several offers from families in Spain and France for the summer hols. If you’re in the Lakes you’ll have no problem finding someone to exchange with.
Basically you draw up a simple agreement so each party is clear on what is expected of them in terms of bedding, cleaning, key arrangements etc. Some exchanges also allow use of vehicles but that’s entirely up to you. Obviously you need to inform insurers but they’re generally happy as they’d prefer the house to be occupied whilst you’re away.
Example here: http://www.guardianhomeexchange.co.uk/ihea/houseinfo.cfm?id=28537