I can't seem to find Darren's thread, but there are a couple here which should help:
viewtopic.php?f=3&t=3604&hilit=+weylandviewtopic.php?t=880&highlight=shock+troopsJacket is a white N2B parka (or at least based on one for the film- for all intensive purposes it would be easier to get an N2B rather than have one custom made).
Trousers are A-11 flight trousers.
Padding- if it wasn't actual cricket padding, then cricket padding would be close enough.
Helmet and backpack will have to be scratch made. Or you could buy one of Terry English's helmets... how much were they again?
Hope this helps!
Kevin