Hi Ian,
The reason your oven is tripping i think it is because the elements have got moisture in them due to the cooker being standing for a long time. if the Teka HT485 oven has been kept somewhere dry but cold sometimes the damp can get into the elements. you could try taking them out and putting them in anther oven for a few hours on hi heat to see if you can dry them out.
But the only way to test them is with a meter called a megger, a "Megger" is a high-voltage insulation tester and not something that most people have. if you find that one of the elements are faulty i have put a link below to your Teka HT485 oven where we have the parts listed there is also a quick video to show you how to test elements to see if they are open circuit. there are also many videos in the repair guides to help you replace elements or just to take them out.
