Hi to you from David. 'The Famous Forry'
Have you got a multimeter?
Often the fan assisted 'Circular' oven element fails and causes trip out. Assuming you have wired grill element correctly , I would look at any other element, starting with circular fan assisted, usually hidden by back plate inside oven. These are easily replaced and relatively cheap. There are other ways to test if you do not have a multimeter (available B&Q and all other good DIY stores for as little as £5). Just come back to me and I will talk you through the process of elimination. Thanks regards David.