After succeeding in getting my Milly through its first MOT here are my lessons learnt from the experience.
Firstly it was not as bad as I was expecting it could be. Trying to get clarity from various agencies was a battle until I finally got talking to the right people at DVSA, that's the tech folk at HGV tech.( HGVTech@dvsa.gov.uk ) They are approachable and helpful.
Filling in the VTG1 (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/6