We checked a few sites. One gov site was saying I was fine due to the expiry date and another said I may have issues.BTW @Dan Baillie - the same site (https://check-passport-for-travel-to-europe.homeoffice.gov.uk/) says travel to Cyprus for my son would also be fine based on a passport issued 4 years and 8 months ago. BA site directs to the Gov website.
they need 3 months clear as a min.
I also spoke to Eurostar who said it may be fine but depends on who Is checking so there is risk.