I made it a while ago, and from memory I followed the recipe (which can be found here) pretty closely. I recall substituting mixed spice for the cinnamon - I feel that cinnamon is sometimes overused - it has its place, but mixed spice gives a more complex flavour that I enjoy more in this type of cake. And looking at my photographs I'm not sure that I made it in a 7" square tin, I might have used an 8" square and reduced the cooking time a bit - my cake looks much flatter than the one pictured. I don't think you need as much icing sugar as listed if you only want to make a drizzle type topping - mine covered the cake easily, which didn't really matter - I suppose I could have made it thicker if I'd only wanted a drizzle effect.
I really enjoyed this one - I can almost kid myself that it's healthy with oil rather than butter and all that veg.... Anyway, colleagues enjoyed it and one of them remarked on the use of mixed spice rather than cinnamon, which pleased me greatly! I think that on balance I prefer this cake to Delia's version. Although Delia's is lovely, a couple of times I've made it, it has been bordering on wet rather than just moist, which I found unpleasant. This one is lighter but still moist whilst still containing plenty of carrot and raisins. Yum, perfect with a cup of coffee.