Troubleshooting faulty electric oven
I had the oven tested by a professional and the cause was the function control switch[1], which the knob is connected to. Looks like a connection inside of it had broken due to wear and tear. It's been replaced and the oven is now functioning as normal

[1] http://www.partmaster.co.uk/cooker-oven/ae6bfs-5400157560/oven-function-selector-switch/product.pl?pid=3262627&amp;shop=bush&amp;path=592111&amp;refine=function+selector+switch&amp;model_ref=2595974