Wow, a lot to go on, many thanks.
My plan was to use a flatbed scanner, 15mm apart keeps nagging me and don't know why, trigonometry not my strong point here, 10mm centre-to centre seems too close, beginning to think I should half that distance as wilfred indicated.
I did expose a pcb once in Sunshine, was just before mid-day about 11.30 around May or June... I let it stand for 8 minutes it turned out perfect and I used inkjet film with two copies taped together AND I did use a glass plate to keep the film flat so glass was no problem there, I was quite surprised it worked, no trace problems or nothing, going back a few years now mind.