Chris,
I have road registered many vehicles, 2 x CVRTs, Ferret, Fox, 432, Land Rovers etc. It's fairly simple. I suggest you contact Footman James, http://www.footmanjames.co.uk/ , they should know what a 432 is as they insured ours. Insure it under the hull number, found on a small plate welded to the hull on the left hand side of the rear door, or use the army reg no.
To drive it on the road you will need to register it with the DVLA. Hopefully you have the cast vehicle form, which makes this process dead easy. You will need to fill in the relevant form, I forget the number but V55 sounds about right, and take the cast vehicle form along with the insurance certificate to a local dvla office. They will take about £50 off you and in return give you a form allowing you to have number plates made, and a tax disc, which will be free for a 432.
If you have any more questions or need help filling in the form let me know.
Chris