BalbyJoe was correct: just use a knife or screwdriver to lever the two sections apart. You don't even need to remove the door from the dryer: start at the top front (open) corner and work to the bottom, then toward the back top and bottom. You need a torx T10 to remove the catch. Note which way up the original catch is (there's a sort of bit of webbing): on the WTA 3100 the hook points up.
The cheapest I could find the replacement door catch was about £6 (~$10) including P&P etc. on Amazon (surprise better even than E-bay). This is still a huge amount of money for something which obviously brakes regularly (especially in cold weather). Bosch should really give them away with fitting instructions, to maintain their position as a quality manufacturer.
One last thing: to use the dryer without the catch: you can reset the door release mechanism by pushing a teaspoon handle quite hard into the hole. Then just hold the door shut with anything: I used a window cleaning sponge with an extendible locking handle (sponge against the door other end of the handle in the corner between the floor and cupboard opposite.
Randall, January 2010
