When you mention courses, are they the standard week long jobs done in fareham? or are they Civvy courses? If they are the latter they should give you everything to pass the course (apart from reading up the material as homework). If it is the same ones I did for a sys Admin role on a couple of comms systems they do provide a grounding.
You can sign up to various internet sites which do a 'question of the day' which are good for revision.
If you are persuing your exams as part of your resettlement, have a word with the resettlement office, you may be able to get them to provide you with the publications associated with it (Prep Gold for ..... books, I was able to sign one out for my CISSP revision. they do others).
I looked at CEH, I did not have the appropriate techie background, have you been involved in Penetration testing? Experience again is normally required by companies. The life of a Pen tester is a lonely one with a lot of time spent on the road and living in hotels. ( no sympathy for them as they get paid oodles with experience). If you are at the tri service base near Bedford that does the RNITSO course see if you can get hold of someone within the RAF test team based in Digby.
Your ITSO ecxperience is useful as a indicator of your ability to enforce procedural security on IT systems. If I had my time over again I would have used my ability to get hold of The Manual Of Protective Security (HMG), the 440 is subordinate to this, not easy to get hold of from a civvy contractors point of view. Look into CESG memorandum, some of which are NPM and can be downloaded off the net.
MCSA/MCSE are always a good route to follow if you have the background experience, from your profile you may well have. There are 2 modules within the MCSE that are security specific as well.
Have you any UNIX experience or knowledge. If you do it is handy to mention on the CV, potentially look at one of the UNIX + type of exams or something a bit more in depth. UNIX/LINUX and the other flavours are an up and coming area.
If you have any contact with companies which are providing tech assitance or implementation get info from them. Networking is the buzz word, and it works. They may even take a copy of your CV. Most companies pay a bounty to staff who find people which they can employ. It saves them money in paying for Recruiting agencies.
A bit disjointed in answers and guidance but I will try to give you a lead if I can. A lot of people helped me before I left, so its good to give some pay back. Its not a hard life being a IT security Consultant trust me! Just busy at times