I've found an old (Ford Sierra?) fan that's much thinner than the VW one, at 9cm thick. After attaching it to the radiator, it *just* fits under the bonnet, with around 1cm clearance at the top left and right edges, close but good enough for me!
By test fitting the lights I've drilled just about every hole I can think of in the body before the car goes off to be sprayed - two weeks today!
I don't have much spare time at all between now and then, so sorry if the updates slow down.