Thanks for all your replies. It looks very much as if my initial scepticism was justified. I'll stick to the old box, and continue to have it serviced annually.
I have a Potterton Kingfisher CF50A boiler which is older that the 23 years we have lived in the house, and which has been serviced annually by a gas-safety registered engineer and has worked very reliably all that time. This year I had to ask a different registered gas man to do the service...