If you have been legally working in France youcan use Class 2 Contributions to top up your UK pension.
The cost far less than stumping up Class 3 Contributions.
However, there is a “Catch 22”.
The Department of Work and Pensions will only deal with your request when you are within 6 months of your official retirement date (many female pensioners have already had their reiterment date put back by several years)
On the otherhand Her Majesty’s Revenue & Customs (HMCEC will charge you an increased amount if you don’t pay you Class 2 contributions as early as possible.
According to the HMRC this matter is with their “lawyers”. The HMRC adcice s to pay the higher amount and to ask at the end of the tax year whether the payment you made is correct.