Clearly are scammers, wow!!!
Do you really need a certificate?
Definitely better out and let your GP manage you instead. I wonder if your GP would be preferred to do what mine is doing for me, a straight forward referral to an endo, especially if you have an existing hormone imbalance, might be worth asking?
Personally, it's never given me any issues swapping from one regime to another, so I'd just stretch out what E you have and then switch straight to BO