You are all being far too kind to Fear with your suggestions, he would have to be played by either Richard Fairbrass or, my personal favourite for the role, Richard O'Brien.
I'm claiming Vin Diesel to play me (he'll need to fatten up for the role a bit though)
Trekker will have to be played by David Niven (might be in need of a time maching here)
Deano can surely only be played by Sacha Barron Cohen (in his best Borat get-up)
Skeggy has to be Dolph Lundgren
I want the brain surgeon to be Richard Wilson whom, a few minutes after the first incision exclaims, "I don't beleive it!"
Mike Field can only be played by Tom Hanks - think Forest Gump when he was running accross America and grew out his beard
Randystand - Alan Carr (Sorry Simon but I just couldn't resist)
BBJ - John Wayne (we really need to get that time machine sorted out)
I see Body Butter being played by Russell Crowe in his gladiator days - being an English teacher he surely speaks in the same way and would simply kick the but of anyone not performing in class to his standars.
Heathfieldroad - Dustin Hoffman (as Rainman)