From reading
GCHQ by Richard Aldrich. Lots of intelligence related stories going back 80 years, well worth the read.
Foreign help regarding the Falklands:
Portugal offered use of the Azores for refuelling under a treaty dating back to 1373.
Spain blocked a covert attempt by Argentine forces to sabotage ships in Gibraltar.
Dutch listening sites at Curacao and Eemnes (previously a US base) passed on intercepted diplomatic and maritime messages.
Germany also picked up and passed on Argentine signals. The code was of WW2 German origin, captured by the French and sold to Argentina....
France passed on signals intercepted at their spy base in French Guyana. They stopped a number of arms dealers who were selling to Argentina. French security forces blocked Exocet missile sales and told the RN how to spot and intercept them when inbound.
Norway picked up images and messages beamed down from newly launched Soviet satellites flying over the South Atlantic and passed them to the RN, helping us track the General Belgrano.
The Sierra Leone government allowed the troopship Canberra to restock and refuel in Freetown. This may have more to do with making money...
Chile secretly allowed British forces to use their bases and provided details of Argentine military forces. A Sea King helo crashlanded after dropping off an SBS force in Argentina, the crew were caught by Chile police and well-treated and sent home quite quickly. It is possible a few Nimrods flew from Chile on recon missions.
The US gave us new versions of the Sidewinder missile and lots of ammo delivered from NATO stocks in Europe to Ascension Island by Galaxy aircraft and plenty of intelligence. There was an offer of a full-size aircraft carrier if ours got sunk, more to do with the NATO role in reality. They also helped stall for time with the famous Haig negotiations.
New Zealand sent ships to take over the Persian Gulf patrol from RN ships which then sailed to the South Atlantic.
And this is just the stuff we know about....