How are house prices doing in France?

We are looking at spending a portion of the year in the south of France, either Nice, Beaulieu or Villefranche and were wondering if renting or buying would be best.

We have two rental properties in London, both of which have offered great investment returns and have been fairly hassle free.

We had thought that buying in France would be best, but I'm wondering if we would be better buying another property in London and using the rental income from that to rent a place in France?

I guess the decision would be based on which place is likely to make more in the long term, and I think London might be the best bet?

Obviously markets can go up and down, but is the London market likely to be a better long term prospect? Are there any other factors I need to consider?