So here we are, apologies for the delay
All measurements taken on the LHS of the car, but should be symmetrical.
From rear of boot lid edge shown - holes approx 22-25mm and 140mm from rear edge of bootlid
Distance to side of bootlid, rear (of car) hole, 45mm:
Front (of car) hole, 55mm:
Centre hole is central side to side, and 30mm from rear edge:
Hope that helps
I can't guarantee the mounting holes on my car are original so may be worth double checking against your spoiler that they make sense!