They're not cheap either (£30.92 and £7.81 + VAT in 2008).
Mine (S2) never shut or opened very well but I found it helped if I lifted the whole box up until....... the barrel of the lock fell on the floor. It's been in the ashtray until today and I've had it to bits. What a pile of crap!
The barrel has four flimsy levers which are aligned by the key. In the RHS of the barrel, there is a ~2.4mm diameter hole, approximately 5mm deep. I eventually fished out a ~2.4 mm x 10mm roll/spring pin from the lock mechanism. This is obviously why the barrel fell out, so I replaced the barrel and inserted the roll pin with tweezers from the side of the lock (with the latch pulled up) and pressed it home.
Nothing. Pulling the latch didn't release the catch so I fished the roll pin out and did some measuring. There is about 5mm from the outer diameter of the barrel to the catch release mechanism which is the distance the roll pin sticks out!
No the wonder the damned thing doesn't work very well. I think the roll pin must not be pressed fully home to enable them to engage - so either too far in and it doesn't release or too far out and it drops out.I can't find them anywhere - does anyone have a 2.4mm x 12.5mm or 3/32" x ½" or do I have to get agricultural with an angle grinder?
Thanks for looking Dave. 
Let me know either way mate.
