Hi Hugh Rhodes,
Article 18 of the UK / France tax treaty gives full relief on UK pensions being paid to a resident of France. The pension will be taxed initially, until we receive a validated DT individual UK / France, which can be downloaded at
Application to claim relief at source from UK Income Tax and repayment of UK Income Tax. You should complete the form, declaring all the pension you are receiving, including state pension (if appropriate) and send the signed and dated form to your local tax office in France. The French tax authorities will validate the form, confirming the pensions are taxable in France and sent the validated form to you, so that you can forward to HMRC at the address on the front page of the form. From this, we can arrange for your pension provider to stop deducting tax and repay and tax deducted in the current tax year.
Thank you.