Not quite true that he was almost unknown in the UK. The BBC showed a clip from an Esther Rantzen programme from back in the 80s or 90s when an invited audience from among those who had been on his Kindertransports in 1939 were recounting some of their experiences. Rantzen said -"If any of you owe your life to Sir Nicholas would you please stand up". Everybody stood up!
I knew about him before but had no idea he had been in the RAF, so I thought it might be interesting to post his war service, taken from Wiki
Winton originally sought registration as a conscientious objector and served with the Red Cross, but in 1940 he rescinded his objection to join the Royal Air Force, Administrative and Special Duties Branch. He was initially an airman, rising to sergeant by the time he was commissioned on 22 June 1944 as an acting pilot officer on probation. On 17 August 1944 he was promoted to pilot officer on probation. He was promoted to the rank of war substantive flying officer on 17 February 1945. He relinquished his commission on 19 May 1954, retaining the honorary rank of flight lieutenant.
A very brave and humble man. Somebody said it was a shame that Spielberg hadn't made a film about him, as well as Oskar Schindler, but I doubt if he would have wanted it.