Had a bash at putting the decals on. Decided to use my mate Plastic Fan's method. Painted the area with a gloss coating and when it was dry I applied the decal on that, using Micro Sol. When the decal was fixed in place I applied another coat of the clear gloss to seal the decal in. The next stage is to use Dullcote to remove the glossy look, but I haven't got there yet.
The decals are from Skytrex. There may have been a tank called 'Black Jack' but if so, I don't know if it was a male or female, and I seriously doubt the lettering was this size and in this position. However, I don't care! I think this is a good name for a tank and I like the sound of it.
I've also given the tracks a wash with a dark rust colour, and I did the Tadpole as well: