Good to hear from you again. The Hohner Holborn you have just added is very similar in body shape to a Grimshaw Meteor dont you think?
I have emailed Paul Day about the Giles pickups but have not, as yet, had a reply.
In answer to your question re first electric Grimshaw, you will be surprised to learn that it was 1937 that they first listed an electric guitar which could be played through a special amplifier or a radio (according to the catalogue). This guitar was made from parts imported from Rickenbaker in USA, although some parts were made in UK (including the amplifier in the case). The first Grimshaw electric guitar was 1948 this was an archtop (called a Plectric) which was modified to take a pickup in the neck and switches and controls attached to the scratchplate (Grimshaw applied for a patent for both in 1948 and was granted in 1954, which means it only ran out in 2004). This system they used a lot until 1960. The first purpose made electric was the semi acoustic SS Deluxe in 1957. Hope that helps.
I just love these later solid body Grimshaws from mid 70s to mid 80s, they are really unusual and are still very capable guitars today. See the photo (to the right) of two Grimshaws which date from 1978 and 1980, both bought new and the owner still gigs with them in his blues band in Northampton. I have heard them and they are a great blues band and the guitars sound as good as any yankie guitar!! They really would make anything you wanted as they were desparate for any work by 1980, even advertising refrets.
Look forward to hearing from you again soon.