Thanks MIJ_Jagger.
I've been doing more searching and reading on the forum.
Did you take the 12v supply from a switched live fuse from the fuse box and does this prevent any battery drain issues?
A Google image search shows a couple of different ways of connecting a wire to the fuse box: some shoe a wire possibly with a clip on the end goicng directly into the front of a spare fuse slot while another shows a fuse carrier spliced into the path from the fuse box to the adapter.
Can the live wire go straight into the fuse slot with the fuse removed without any problems?
Thanks again, in advance.