With only HNC I'd argue that you're in a bit of a difficult position - you aren't really looking for a job, you're looking for more training. The question is, as what?
I'd suggest that from where you are you need to go one of two directions, depending upon whether you have an aspiration to wear a suit and do difficult analytical problems, or wear overalls and solve difficult maintenance problems.
Either....
(1) Start looking hard at apprenticeships: e.g. BA, BAE, Qinetiq, AgustaWestland....
(2) Apply for a place on an appropriate degree: e.g. Aerospace Engineering or Mechanical Engineer, somewhere like Southampton, Brunel, Sheffield, Glasgow...
With one of those behind you, you can really start looking for that REAL first job.
G