I've also had a couple of e-mails fom other forum users that helped clarify a lot of things as well so my thanks to all.
I'm left with few questions.
1. Most images of Mk.I's feature a large box at the centre of the rear plate above the axle, I'm not sure what it is but there seems to be a fuel or water can rack fixed to it as well... What is it and is it a standard fitting of the Mk.I?
2. There is a large and complex floding arial mount on the offside rear of the main compartment, how common was this mount? It looks to be quite complex and I'm not sure my scratchbuilding skills are up to it in 1/48th!