Here's the UK CAA guidance page for initial class 1 medicals.
https://www.caa.co.uk/Commercial-ind...l-certificate/
As it's the UK CAA, I would be inclined to verify with the individual Aeromedical Centre. But basically, its only in and around London -
Despite what it says, I don't think NATS at Swanwick does them - for the same sort of reason as NATS at Prestwick apparently stopped some time ago.
The Aviation Medica website mentioned above is here.
Aviation Medica - Services
Good luck
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