Hi Tim,
Unfortunately HSBC as you're probably aware used to do the CTC wings cadet loan. However this has now stopped much to my expectant disappointment when I saw them not so long ago.
This means that the only way to pay the security bond now is by funding it yourself. This can be either through having that sort of money laying around in your bank collecting dust or through obtaining a secured loan against a property. Usually Mum or dads house. Although this can still be quite straight forward re-payments are due instantly so some one will need to start paying them back. It can't be you as you'll be training for 18 months on nil salary approximately.
Alternatively sell your mum / nan / dad / sister for what ever you can get for them.
Sadly this credit crunch has had really hit those that are pursing the CTC route. However CTC are apparently talking to other banks to set up other schemes. Sadly this could take quite a while and it could be any major high street bank.
I can't offer much advice as I don't think anyone really knows what the best thing to do right now is.
Good luck with the selection though.
Chilli.