My grandfather was born in Argentina of French descendents... when the Spanish civil war broke out he fought for the International Brigades against the fascists. When the war ended in '39 he went back to Argentina and then came back to the UK in 1940 or '41 (we're not quite sure) and then due to his French background joined the Free French, flying for the RAF under the flag of the Royal Canadian Airforce.
It's all a bit convoluted so I'm a bit clueless to where I should start. Can I get records sent to me or access them online or will I have to go to the National Archives?
Any help would be gratefully received.