This blog post may answer that topic: Do FPV UK members require an A2 CofC? - FPV UK
This one minute FPV UK video also addresses the topic: Recreational drone pilot? You don't need an A2 CofC! FPV UK Article 16 Operational Authorisation. - YouTube
If, after all that, you still want an A2 CofC (Perhaps you do commercial work with your drone from time to time), FPV UK members qualify for 50% discount on an A2 CofC from UAVAcademy. See your Member Deals section for the discount code.
I find the a2 cofc usefully for adding lights. So I go over the 250g limit and I’m loud to go up to 500g but with no intentional over flying people. This is the only advantage I really got out of having the a2 cofc. We lost all the c class rating so we loss the main purpose of having the a2 cofc. This is old news now.
The fly in city’s with a 50m horizontal separation from uninvolved people makes this useless in the city. So it an odd qualification. I only got the qualification because people said it would make me flyer safer. What a load of ruppish it did showed me I was safe flyer already so I guess it did give me more confidence in my decision making process.