In the Proxy Accounting page when trying to enter an address the page will only allow numeric postcodes with no spaces. The Netherlands and Great Britain both use alphanumeric postcodes with spaces.
Also found that the Bank Code only accepts numeric entries. The Bank Code in Great Britain (known as the sort code) consists of three groups of two digits separated by a hyphen. Patch created to deal with these found limitations and submitted to the dev mailing list and patchwork. Confirmed to work in a vm setup. https://patchwork.ipfire.org/project/ipfire/patch/20220218143352.5927-1-adolf.belka@ipfire.org/
https://git.ipfire.org/?p=ipfire-2.x.git;a=commit;h=ab50bf41fec93cf480e66140d2161580f4d72926
https://blog.ipfire.org/post/ipfire-2-27-core-update-165-is-available-for-testing
Confirmed on Core Update 165 Testing that the post codes and bank codes can be alphanumeric now.
https://blog.ipfire.org/post/ipfire-2-27-core-update-165-released