Hi Phil,
Lived here in France for seven years,and seen a few come and go after thinking that they could make a fortune/living from "doing up" a wee barn and selling it on.The cost of using artisans (tradesmen)takes out any profit.They have to pay so much and so many taxes they are not cheap.Doing it "on the black" (using unregistered tradesmen ) is not an option they and you could be jailed for 5 years and fined 10,000 euros.Also the taxman takes a great deal of interest in what you are doing-we have had seven visits in two years whilst in this house.The locals are keen to know your business and we are told that the postman etc. gets a reward from the tax man if they report any building work that is not registered.Building materials are no cheaper than the UK.The planning process is easy and building control does not exist(for renovations)They love their red tape and everything has to be stamped and then stamped again.They are very keen on foreigners following the rules,even if they don't quite understand the rules themelves.The lead time for ordering items varies daily.
Depending on the scale of your project and your capabilities then I would say that the DIY route is best,however the property market is suffering here as well as everywhere across europe.So doing up to sell on is still a gamble.
Finally,speaking French is a must.I know that that may sound obvious but you will struggle if you cannot communicate.I tried shouting in English but that don't work
even when they can see the lintle is falling,they will stand and watch it fall on you.
Hope this helps.