If the oven is tripping the electrics out when it gets hot then its going to be a faulty heater element. Its more then likely the main fan element as thats the one that usually fails and causes this fault.
If you are getting an engineer in then give them the model number of the sticker on the inside of the main oven door and hopefully they will bring one with them.
But if you want to find an engineer to fix it for you then let me know what area you are in and i will see if i can find an engineer for you.
Im afraid we cannot book it in for you. If you give this number a ring first thing in the morning then hopefully they will book you in. Its 01473 690033.
They are called Ipswich Oven and appliance repairs.
Im sure they will sort you out and get it up and running again for you.