Phileas
You almost sound conspiratorial. Mrs T did what she had to do at the time.
I wasn't aware there were any RM's on South Georgia at the time, just scientists.
The American's thought that any Argentine 'posturing' was going to be directed against the Chileans over disputed parts of the T de F.
HMG knew of the Argentines 'desires' towards the FI, hence the deployment to the area of 2 RN surface ships & a nuclear sub' in the mid-late 70's, but perceived it as 'Latino Bluster', especially since Argentina & UK PLC enjoyed cordial-good relations with a plethora of military trade deals immediately prior to April 1982.