There are some Brits here for whom, economically, times are really hard. They are the ones who relied on either working (even the French can't find work) or living off interest savings (which have plummeted to zero). When things get really desperate and the outgoings exceed the income - like Mr. Micawber in Dickens - there are basically two options. You can either go back home to the UK and stay with a relative whilst looking for a regular (all-year) tenant for your French property, or consider downsizing in France.
For the latter, you can usually get a French bridging loan for 70% of the value of the existing property, which you can use to buy a pretty village home in France - there are loads of cheap properties available all over the country. These loans are normally granted for a period of up to two years which can be extended in some cases, but you don't need to pay it back until your original house is sold. In the meantime, you put your original property on the market at a realistic price and when it eventually sells, you pay off the loan and bank a large cheque.
Of course, you need to take account of all those extras, like estate agents' and notaires' fees. There is no standard agent's percentage - you need to check out the rates in their window. Certainly avoid those who charge more than 8%. A cheaper way of selling is to do it via a notaire. They are required by law to stick to a standard fee, which is always cheaper than an agent's fee: 5% of the selling price up to 45,735 euros and then 2.5% thereafter plus tax. Details of properties on sale via notaires can be found at http://www.immobilier.notaires.fr/.
The rule remains the same here: secure a regular income (it doesn't have to be large - we've found that you can live quite well on 1000 euros a month). The sun is shining, the air is clear and life is good.