Well, I have made it a few times (well loads of times actually) since and it's delicious.
Anyway, I decided to make it yesterday and have a bit of an experiment. So I put a pear in the oven with a handful of frozen berries for about 10 mins and then kind of smooshed them down, and added that to the final mixture, after draining off the excess liquid.
I also added probably 1/2 a teaspoon of cinnamon and a sprinkle of nutmeg and put some walnut bits on top.
Oh and I also added probably a 1/4 of a teaspoon of baking powder in case the extra liquid made it not rise - I have no idea if this was necessary though.
I'm just having a slice now and it's lovely.