Valiant boiler showing F64?

Hi - Our Vaillant Eco max boiler 824 was not giving any hot water this morning and showing code F64. I phoned their helpline and the technician said that means the electric circuit board is damaged and needs replacing. this will cost £285 if repaired by Vaillant. Our boiler is 13 yrs old at least - would we be better off getting a new one - British Gas are offering £400 off new boilers if you trade in your old one. Will still cost loads of money to get them to install it.. We now cant turn the boiler on at all.. wondering whether to pay for a quick repair or to wait ten days until British Gas sends an assessor to see if we are eligible for their deal.