Looking at the list of ingredients they contain a very respectable 40% of fruit – currants and raisins – and no hydrogenated fats – so they must be good for you, right? (Except for the 9.1% butter but fortunately they don’t put the calorie count on the pack).
You need to heat them to enjoy them at their crumbly best, easily accomplished in the Aga, but otherwise I’d be inclined to do that over a low heat in a covered pan rather than faff around heating up the oven.
The website reveals that the Lancashire Eccles Cake Company is a family owned firm which has been making eccles cakes since the 1930s which is rather nice. They even export to the States.