It appears your posting has slipped under the radar of the RAF experts here, so I'll give it bash.
Nothing turns up in the service records that are available online which completely fit the description you provided but on the assumption that he survived WW2 that's not surprising as his service record will still be with the MOD. Unfortunately,you can't request a copy of his service record as you can't prove that he is dead. For the sake of completeness the process for applying is explained here:
https://www.gov.uk/guidance/request-records-of-deceased-service-personnelI have found a reference to a Sergeant Harry Dennis Houghton in the RAF Volunteer Reserve a fighter pilot who was killed in action over France on 28 Apr 1943 (full details on FindMyPast). However this is not the same man, as his service number was 939010.
I have no idea what A6458A refers to. It looks like a Unit Identity Number but that doesn't really get us anywhere.
As for his birthday, surely 2 to 3 weeks from 20th April puts it in mid May rather than July/August?
Nothing obvious turns up for a Harry Houghton in the Lowestoft, Uxbridge, Gloucester or Penarth areas in the 1939 register, but I imagine you've already tried that possibility.
The only other thing I can suggest is that you go on one of the many RAF old comrades forums (eg
https://www.facebook.com/RAFMSVA/ ) and see if his name rings a bell. Quite a long shot I admit, since most of his former colleagues will now be dead, but his name may just crop up in some reminiscences or in the unit entries in old RAF journals (
https://www.rafmuseum.org.uk/blog/perusing-periodicals-in-the-raf-museum-library/ )