CGNAT

Apologies if this question has been asked before.

Does anyone know of a UK mobile broadband provider that doesn't use CGNAT?

Either consumer or business would be fine.

It's only required for a few months, so a 30-day contract is preferred.

T.I.A.

Three, if you use the right APN ("3internet").

Though I've seen a suggestion that it doesn't apply on 5G and you are stuck with CGNAT there.

Very pricey, but AAISP do fixed static IP SIMs https://www.aa.net.uk/voice-and-mobile/data-sims/