adverts on tv with the Jolly Green Giant (I think) teaching children how to cross the road....Never Cross the Road without the Green Cross Code

Certainly not the US Green Giant, rkay, though he is certainly Jolly, being inclined to a "Ho Ho Ho" rather than a "Fe Fi Fo Fum" (and incidentally partial to sweetcorn niblets rather than bread made from ground-up bones).

You're thinking of the Green Cross Man, a superhero played by none other than Dave Prowse aka Darth Vader.

Check this out:
http://www.toysrgus.com/images-speci/harper/prowse-greencross.html