Hello Paul,
No answers from anyone, it's almost as if these vehicles are rare. I did find a picture on the web, posted below, but I think that this is a post war box from another vehicle The owner of the vehicle resides on the HMVF web site but doesn't respond. To be honest, I wouldn't be able to get a box over mine unless I moved the battery tray towards the passengers seat. As you can see from the original floor panel, that's the rusty one, the tray is over towards the drivers seat and there is no evidence of it being moved to that position.
I haven't had any luck with the information plates either but I do have the means of replicating them when it becomes available.
I hope that the chain cores your oil leak, so far the only leak from mine was where some idiot forgot to tighten the sump nut.
of course its early days.
Keep sane,
Jonathan