Ok, can you advise which lights are flashing on the oven, and the model number of the oven.
E8 is a communication fault between the main control board and the display board.
This may be caused by a lose ribbon cable, a failed control panel or display board.
Unfortunately this will require an engineer to come out and strip the unit down, worst case a new control board would be around £150, but in most cases its a case of just reseating the cable.
If you would like me to recommend an engineer to come out, please provide your postcode.
No problem, I would suggest you use OCR their number is *****(###) ###-####
They will come out and give you a non obligation quote free of charge, we have referred a number of customers to them over the years and have always had excellent feedback.