Baked on a pizza stone
Proving in airing cupboard
Proving and water to recipe
Starter had been fed lots over the week on advice from pastry chef at work
First off, as Reynard has already pointed out, an airing cupboard is too warm. I prove mine where I can see it, on the coffee table if I am reading or on the kitchen table if I'm doing other baking stuff. It is never out of my sight and I check it frequently. Unless you're baking to a tight schedule, time is your friend and you want things to be slow -it improves the results.
Proving and hydration to the recipe sounds like the right thing to do but no two kitchens are the same, heck , the recipe might even be from another country with a different climate. If you followed it to the letter then it doesn't work for where you are (assuming you didn't overprove it in the cupboard) so you'll need to make adjustments.
I feed my starter several hours before I need to use it. Once it's foamed up like a huge aerated marshmallow it's ready. I can tell by looking at it but a good test is take a spoonful of it and place it in a glass of water. It's ready if it floats.
I can't add a lot more, you need to experiment by adjusting one aspect at a time to see what happens. But I recommend you go by look and feel over timings. Your dough should go into the oven while it's still on the rise and feels springy. If you press it with your finger and it doesn't bounce back fairly quickly, you've overpoved it.