ExSp33db1bd
The book "Stand by your beds" by John Hamlin lists National Service numbers.
Yours falls into the batch 2700000-2787999 allocated July 1953 to Feb. 1956. 88,000 in all and all non ATC.
I was 5011609 in the batch May 1956 to an unknown date. ( I went in 1 May 1957 ). A total of 1334 in that batch and all ex-CCF(RAF). Not until I read that book did I have it confirmed that there had been separate numbers for ex cadets - although it had been rumoured.