If it wasn't for greedy locals selling houses to outsiders, there'd be no housing price problem in any of the tourist areas that bleat on about it - Cornwall, lake district or wherever.
You can just imagine the scene at the estate agents:
Cornish Local: "Both my parents are now dead, they left me their house so I'd like to sell it please"
Estate Agent: "OK, how much do you want to put it on the market for?"
Cornish Local: "How much is it worth?"
Estate Agent: "Well, there's this bloke in London who wants it for a holiday home, he'll pay you £300,000"
Cornish Local: "Blimey, my mum and dad only paid £500 for it, but I suppose that was a long time ago. Hang on though, seems a bit of a waste the place only being used for weekends. Are there any local people looking for houses?"
Estate Agent: "Oh yes, there's a lovely young couple, just got married, looking to move into a place of their own. Both of them are Cornish, work and live locally"
Cornish Local: "Awww, that's nice. How much are they looking to spend?"
Estate Agent: "Well, he's a mechanic at the local garage and his wife's a teaching assistant. They can afford about £100,000"
Cornish Local: "Sod them then, I'll take the £300,000 from the stupid emmit, pay off my mortgage and buy a speedboat."
Nobody is forcing Locals to sell houses to outsiders, they are choosing to do so because they get more money that way.