I'm still looking for harnesses for someone asking on here, so much stuff.... found this so far:

Willans 3-point in blue, as pictured.
Unsure if I ever used this on anything, but by the looks of it, I haven't... I can't even remember what car I purchased it for.... old age I guess. I need to make some tie-downs, but before I cut it up....

£20 plus postage sounds very good to me (or you can collect).