OK getting to the bottom of this remote boot issue now...After talking with Mark and Kim at Hopton Garage MG..who provided the attached picture from the workshop manual.
The 2012 and 85th Anniversary TFs have this fitted as standard and the extra bits needed to retrofit to earlier TFs are:
1. New boot lid..as the metalwork is different around the boot lock to accommodate the solenoid. Basically the catch box which is spot welded to the boot lid is extended and drilled to mount the solenoid.
2. Solenoid..from a Metro GTA..supposed part No. FUG000070...although no-one including Rimmers recognises this part No.
3. Different catch mechanism incorporating a tag for the solenoid to locate onto
4. Additional loom and external relay...to feed the earth pulse from the SCU through a relay to the solenoid
5. Reconfiguration of the SCU to enable remote boot unlocking
Recommendation from Kim is don't bother..he has investigated doing this and ended up with an after market kit..It was too difficult to reconcile the requirement for a different boot lid.
I'm not sure that the existing boot catch box can't be modified to accommodate the solenoid..Likewise the catch..will consider further and feedback if I decide to progress....Would still prefer to implement an OEM solution rather than use something so obviously aftermarket..but...