Hi MARK,
Article 15 of the UK / France tax treaty confirms that your employment income is only taxable in France, unless you are physically carrying out your employment in the UK.
Article 18 confirms that your pension will be only taxable in France.
This includes your lump sum.
DOUBLE TAXATION CONVENTION
So that you can arrange for your UK private pension to be paid free of UK tax, you will need to download.
Double Taxation: UK-France (SI 2009 Number 226) (Form France-Individual)
Complete the form, detailing your pensions and send it to your local French tax office for validation.
The French tax office will return the validated form to you, so that you can send it to HMRC at the address on the form.
Thank you.