OK, another small update. So I phoned an other dealer in the other direction, and they recommended and "Investigation" @ £144+VAT (£172 inc. VAT). This includes labour (1 hour), and includes
any updates. More labour time if the updates take longer.
The guy on the phone appeared to be familiar with the ECM diesel update, but went off to chat to a service guy, and came back with the "Investigation" recommendation.
Three dealers, three answers