I used to work for the RACV here in OZ as a breakdown patrolman. The RACV is basically a motoring organisation that does everything from political lobbying though to insurance, travel agents, emergency breakdowns and authuorised repairs. I assume your AA is similar.
Now like all of these large organisations with many tentacles, they are top heavy with all manner of clowns who don't have a clue as to the more practical aspects of the business on the ground.
The likely hood of finding anybody in the organisation who would know anything about proper routine procedures and best practice on what is to them an obscure and obsolete car like a MGF, is slim at best.
I have no doubt the there are people there who do know what they're talking about, when it comes to the MGF but the chances of you getting on to one of them are worse than the lottery.
The bloke in the call center (probably working for a call center contractor in Mumbai or some such) will only be going on what would be at best generic guidelines, as he probably has never even seen a MGF or ever waved a spanner in anger in his entire young life.
He is giving you a "no"
answer because he hasn't got the authority to say "yes"
, you need to find whoever has the authority to give you a "yes" answer, that's not always gonna be easy and even then they may still say "no".
So I suggest next time you talk to them, and they start with the "no" answer routine, (keeping it nice calm and friendly) say something like "I realise that it's probably out side your guidelines and as such it's not in your power to authourise this procedure but as it's in both of our best interests to follow best practice and do this procudure, could I please talk to someone who can authourise it?
Many years ago I learned never to accept a "no" answer from somebody who wasn't allowed to give a "yes" answer.