Derek,
You can order a copy of the Marriage Certificate from the General Register Office, as per the following link:
https://www.gro.gov.uk/gro/content/certificates/default.asp
Details of the event : Registration 4th Quarter 1928, Volume 3a, Page 1446
The 1911 Census shows him as an 8 year old schoolboy, living with his parents and sister at 197 Hampstead Road, London NW.
I don't know where you've looked, but 'Dit' could possibly be short for 'Ditto'
As an aside, it would have been interesting to follow up if he had an official National Insurance Number, under either name, but as his death is registered in 1966 he would not have been in receipt of a State Pension enabling a check on which name payments had been made.