Mine has been away for 2 weeks and today I got an email from the technician:
Your MacBook Pro was received and checked in the workshop.
Unfortunately your machine's Logic Board is not covered for warranty replacement under the extended replacement program as the machine consistently passed Apple Service Toolkit's Video System Test which ran a comprehensive set of tests to determine eligibility.
Your computer is not eligible for this repair extension program because it passes these tests.
We did confirm the intermittent fault with your machine's Logic Board and we would recommend pursuing a European Consumer Law claim to have replacement of the Logic Board covered under warranty.
You will need to fill in the Customer Details and Customer Acknowledgement sections of form attached to this email and you will need to provided Proof of Purchase for your machine.
So, rather strangely it isn't covered under the replacement program, but they are going to claim on UK consumer law for it.
They've also identified a dead 'bug' (yes, an insect) trapped in the display and will be claiming for a new display, as it is supposed to be a sealed unit, so the bug must have been there a very long time!