In a previous life I was able to advise potential AIP applicants through regular contact with the desk(s), however I am not in the loop any more.
Best bet is ask the trade / branch sponsor, they make the decisions. Get your previous course info together and send them an e-mail, address should be available if you are connected and can search the mod directories. I believe yours to be located at the college of knowledge in Lincolnshire as opposed to HW.
An alternative source of info may be Flying Training Wing (or whatever their current guise is), also probably still somewhere in the college area.
Previously they were reluctant / not authorised to give an AIP if the training was 'in service', there had to be a large element of personal time involved in gaining the qualification. Thus a course undertaken as a cadet would qualify as the person was not in full time service.
You may be able to generate a suitable NVQ, if you are already out of training you will have rank on your shoulders and can get sufficient evidence of carrying out tasking etc to get to level 4. That can take as little as 4 months and as long as about 24 months subject to your time available. Evidence from your previous employment may be valid if it is within a defined timescale - get up to date info from an NVQ provider. It will cost money to do, but there will be long term benefits as the AIP will eventually get you up the payscales more quickly.
Good luck with it, nothing ventured etc.