thanks for everyones advise - the flour was relatively new (doesn't mean it hadn't been sitting on the shelf at the shops for while given we are in the bush).

MD - this is the first time I can definitely say the oven was well preheated (so often I don't do this when cooking but in this particular instance I did for a change) and didn't open the door.

The house is a rental and we haven't been here too long so maybe it is the oven as this is the second time here with the cake - both times have flopped but the first time I thought it was cause I opened the oven door

It is a very moist mix and I just mixed with a spatula not an electric mixer but because the recipe has said beat for 2 mins at each stage I gave it a good going over with the spatula - maybe too much.

There are a few things there I need to check so plenty of choc cake coming up I think while I test to see what works.

Good tip with the foil thanks Rouge (especially when I'm trying to make a bigger cake cause I've done that before and had the edges over cook while waiting for the centre)

Bath - look forward to reading if you find it Bath cause I've googled and not found too much - they generally focus on the its not cooked and you've taken it out too early scenario.

Anyway thanks again everyone - will update the thread as I go through the testing process.