Baking with oven without bottom heating element

I too have a fan-assisted 230 degree-max oven, and I cook nice crispy-based pizza all the time, thanks to one thing - a pizza stone. Traditional pizza ovens have a stone base that absorbs the moisture from the crust, crisping it properly. A metal pan or sheet doesn't do this, so you get a soggy crust.

Pizza stones replicate the stone base of the traditional pizza oven. They are sized to fit in most conventional ovens, and you can get them from most cook shops, or Amazon, for about £10. Simply place the stone in the oven when you turn it on to preheat, let it get good and hot, then take it out and assemble your pizza right on the stone. Put it back in for 4-5 minutes et voila - a great crispy pizza every time.

You can get wood-fired, stone-based ovens (Jamie Oliver markets them these days) that you have built in your garden, but I'm pretty sure they cost a lot more than £100!

You're baking using a convection fan. This generally won't work unless the cake recipe is calibrated for it; you'll end up with a cake which is brown on the outside and raw in the middle (as you did). It's remotely possible that a combination of lowering the temperature and convection would be successful, but I don't have a formula for you.

Suggestions:

If the issue with top heat is that the cake is burning on top before the bottom is done, I would suggest placing a rack above the one the cake sits on, and a cookie sheet on that rack. This will protect the top of the cake from the radiant heat of the element, causing it to cook only from reflected heat off the sides of the oven. This may, however, increase cooking times somewhat so make sure to check cake doneness with a skewer.

Or: Add a baking stone on the rack holding the cake as well (under it), and preheat the stone for 30 min before baking the cake. This will give it some heat from the bottom.

Or: both of the above.

Or: get a new oven. They make fairly nice countertop ovens now which have a bottom baking element.