What if the UK state pension value drops?

You can request to modify the amount of instalments that are being taken via your personal space

I have both French and UK state pensions. How do I deal with the latter given that its value is affected by exchange rate fluctuations?

UK state pension income – as opposed to a government pension, such as for a civil servant or teacher – is subject to PAS installments once the pension’s existence is known to the tax authorities. 

These will be based on the pension amount declared in your last declaration, which you would have converted into euros at an appropriate rate for the relevant year.

If at any stage you think that your pension income in euros has dropped due to a fall in the exchange rate, resulting in a substantial difference in the amount of tax payable, you can request to modify the amount of instalments that are being taken via your personal space at impots.gouv.fr.

Click Gérer mon prélèvement à la source and Actualiser suite à une hausse ou une baisse de vos revenus. 

A change to the rate and amounts levied will usually only be granted if it is found to lower your annual tax bill by 5% or more when compared with what would have been payable otherwise.