I looked into this last Winter as one Police Ossifer who had stopped me locally a couple of times pointed out that as I was here for over 1 year that I should have a bg card.
So went to KAT and asked them. They looked at me blankly and said "Don't know" and asked that I come back in a couple of days and would find out. So duly went back a few days later and was told that if I only wanted the Car driving bit then they could do it no problem. But I said my card has the small trucks up to 7.5 tons and trailers and minibuses on it. They said that would have to have medical certificate/examination AND a pschological test. I enquired if this was in English like their driving test is meant to be and got the reply that was only in bulgarian but I could take along my own translator. At this point I said that my translator could tell me the answers and they wouldn't be any the wiser. They just looked at me blankly. I even tried to argue that under EU rules I should get a straight swap but they said not. I don't mind the medical test but the psychological test where I have to provide my own translator is pushing it. So I said that would probably be best to leave it for now until they organised things a bit better. Ie test in English or they provide a translator. They agreed strangely enough.
So back to the original posters question. I guess if you provide a medical certificate you will get a standard licence to drive a car which is the norm in UK for over 70. But worth checking at your local KAT as they seem to make up the rules as they see fit and to fit the problem.
Hope this helps