Honda Accord Tourer ictdi - electrical starting problem - asimo

Glow plug warning light not on and car fails to start, at same time VSA warning light on though system not switched off and trip computer clears. Fault intermittent past two weeks.

Dealer couldn't diagnose but replaced glowplug control unit/relay, costly but didn't solve problem. Similar problem under warranty 3 years ago so asked Honda UK for advice but to date no response. Impression that dealer and Honda not interested

Car is 2006, 35k miles, full Honda service history. Any ideas out there