Effinhell, there has been some good advice on here, I'll try and fill some gaps. I don't know what the RAF is planning re CIPD, however I doubt any airman and I'm assuming you are an airman would get full recognition of RAF training to take you up to Chartered membership. Hence I think you'll probably need to undertake some form of training to top up your CIPD membership. In which case I think it's worth selecting a provider which sets its own exams rather than a provider that gets students to take the CIPD set exams, its easier and the training seems to be of a higher standard as well. If you are an officer I know a couple of Flt Lts/Sqn Ldrs who looked at the PAC route, however the cost put them off (£7K in 2000), plus some doubts as to whether their previous experience covered all areas of the CIPD syllabus. Hence I was on a PG Dip course with a Sqn Ldr (I was a Sgt) I'd recommend Bucks New Uni in High Wycombe. With most providers they want to talk to you about your experience, so embellish, if needs be... and don't mention that tour in GD Flt, or the registry.
On the job front, I'm an HR Manager in a Government dept, in fact I got promoted today to MOD B2/Gp Capt equivalent, always thought the Mil/CS equivalancies were rubbish. Anyway I digress, it's tough at the moment outside, you can land a job, however you need to work hard to get the highest level of CIPD membership. I got Chartered MCIPD within 6 months of leaving based on my experience in the RAF. However I worked in personnel policy for 3 years writing briefing notes for AO Plans on why we shouldn't base JSF at Stornoway etc. So be creative and push yourself hard at work, volunteer, pester OC PMS/OC PSF/Chf Clk for more work and make sure you deliver it and do a bloody good job, as time progresses they'll trust you more and more and should give you some challenging work outside your rank. Mention your CIPD studies in you discussions with them, it'll give you credability beyond your rank, very few Admin Sec officers have CIPD membership. This way you get valuable experience and something decent to put in your CV. i.e I lead the PMS efforts to gain ISO 90002 accrediation when I worked in GD Flt as a Sgt, I can now claim to have successfully implemented ISO 90002, be great at change management, continuous improvement and have a sharp customer focus. oh and I helped write the current RAF redundancy policy, now I'm a policy writing god.
Atleast 2-3 years before you leave think about where you want to settle, check out the larger employers, see what they are looking for from their HR staff and make sure you fit the criteria and then some. Tailor your CV, remove all RAF speak, if your non-RAF wife/husband/mum/dad etc doesn't understand it, its written in RAFesse. I lifted common phrases from HR job adverts and inserted them into my CV to make sure I was using the correct langauge. Its worth reading a stack of HR role profiles on totaljobs.com and understanding the language, if you don't know what it means google it, or look it up on CIPD.co.uk. This way you don't look like an idiot at the local college by saying you are a reward specialist when you in fact checked allowance claims and you don't know the difference between PRP and contribution based pay systems
Don't get hung up on job titles when looking for a role, BP are advertising for an HR adviser at the moment, it pays £50-60K, whereas you'll see plenty of HR manager roles around 40-45K, look at the job description to see exactly what's expected. Don't take a job in the public sector when you leave if you think you'll want to work in the private sector in the future, its very very difficult to make the move.
Final words get the best academic HR qualification you can, especially if like me you didn't go to Uni and left school with no qualifications. Nearly 50% of 18 year olds go to Uni, they are the competition, with the same or better quals plus your experience and a can do attitude it'll give you the edge over them, make the effort to push yourself in your last years in the RAF be the guy the Branch Sponsor (Hi John C) doesn't want to leave, be the guy who turns down promotion to FS to take a better offer in Civvie St.
Good luck and PM me if you want any more info.