Jim
GRS www.grsuk.com do sell some body kits which can be built onto LGB chassis. Most of those are to be built on the toytrain Otto chassis, but the Single Fairlie is designed to be built on the Stainz chassis. I guess it might well be possible to fit some of their other body kits onto a Stainz chassis too. That would be worth checking with them.
On the website click
Catalogue > Narrow Gauge Electric Locomotives > GRS Prototype Locomotive Kits
or
Catalogue > Narrow Gauge Electric Locomotives > Freelance Industrial Locomotive Kits
It is worth saying that whilst the kits can be made into excellent models, they are not like air fix models and require a good amount of work from the modeller. The instructions also leave quite a bit to be desired. However I don't know of any other off the shelf solution.
I'm sure it would also be possible to do a bit of work on the stains itself to make it look more British...
James