Well, then you're very very lucky !
I don't think it is the exception. My previous AME only charged £80 for a Class 1. I gave the details of my current AME who is also a forumite.
It does not harm to shop around.
Taking aside the fact that I fly for a living, there is no way that I would change from a JAA licence to a NPPL other than if there was no way I could get a Class 2. For me the freedom of flying is being able to get out of the UK under my own steam.
Saving a few quid on a medical to seriously cripple my flying capability is not even on the option list.