Hi - that's a nice 70s Japanese copy of a Marauder - I had one the same. JHS is distributor John Hornby Skewes, they would have imported this & sold it under their own brand. These days they use the Vintage & Encore brands in the UK, which you'll probably be familiar with!
Anyway, the Japanese ones appear under a variety of brands - yours is the first JHS I've seen, but I've seen these as Avon, Cimar, CSL plus unbranded, which mine was. I'm not sure who made these, it's possible that they were from Fujigen Gakki - some later Cimars are confirmed as being from that factory.
Anyway, here are some pics of mine:







Hopefully that last pic will help with your wiring problem, the only lead I unsoldered to remove the electronics was the earth from the bridge, which I think ran to the earth tab on the jack - the one with the plain wire.
These guitars were very, very accurate copies of the Gibson originals - mine was a great player, too, with an excellent neck & fretwork - quite typical of the better quality Japanese copies.
Jon.