Yabbut 50,000 men is a helluva lot to throw away on a gesture.
"Substantial assistance", yes. Aircraft, some troops, naval forces... But once the Japanese have pushed past 17N, and there is no real chance of stopping them - no more troops and evacuate everything possible (including French troops). Even the French have withdrawn their ships.
Also, a large British army being driven into internment like that? Churchill would, with good reason, fear the British reaction to such a debacle.
I suspect a substantial part of that army would have been French.