Welcome to SF @Alisonjane …
I don’t have an guaranteed answer to your question but would like to sympathise with you for having to deal with Barclays - worst UK bank ever!
I expect someone will be along in a moment with a solution but my only thought is maybe having the pensions paid into an account with Wise and convert / transfer from there?
Wise do a better rate than traditional banks for currency conversion and you can hold balances in any number of currencies, there is no fee for having the account, and they give you a VISA debit card.
My Wise Euro account has a Belgian sort code; not sure if that would be a problem for your French pension.
Anyway it’s a thought, faute de mieux.
ETA: Have a snoop through this thread as well, as someone asked a similar question:
https://www.survivefrance.com/t/french-pension-now-back-in-uk/