Smeg SUK81mf Fan Oven Problem...!?

I have a Smeg SUK81mfx5 range cooker. We inherited the item when we moved into our new house, and the oven never heated up when the fan oven was selected. I ordered a new fan element, and having been advised it was a simple task, fitted it myself with no problems - took photos of where all the wires went etc and double checked everything before switching on. The problem is that now the fan oven heats up, but keeps heating up to maximum irrespective of the thermostat setting. The thermostat itself functions fine, as it does its job alright on the other types of oven setting - and you can hear the switch clicking on and off when you sweep the dial. Any ideas anyone?