Thanks for the feed back guys.
I have, however, come across an unexpected problem.
When I has testing etc I had Defender running and set the switches up to get the credits registering pretty much 100% of the time. Since then I have been trying some other games and am getting varied results. From my list of favorites;
Defender, 1942, Asteroids, Gauntlet, Bombjack, Burgertime all register credits everytime a coin is inserted.
Pacman, 1943, Ms Pacman, and a few others only register about 25% of the time.
I've fiddled and adjusted 'til dawn but the results don't change - does anyone know if some games have a slightly different sensitivity when it comes to coin switches?
When the coin bouces off the "actuator" thing it only presses the button for a split second, this appears to be the problem.
I'm working on a solution that presses the button more firmly (or take eightbits advice and get a softer switch) but would be interested if anyone knows why some games are fine and others not.
I've been having a think about rejecting other coins and may develop this a bit further but it does complicate things somewhat As the system does what I wanted it too (assuming I can sort the Pacman etc problem out) I probably won't kill myself trying... uh oh, the seed has been planted, my brains ticking - aarrhh! - more sleepless nights ...
With regard to UK E-bay I've been checking very regularly for about 8 months now and very little by the way of parts comes up. A few coin doors have been offered but they either had a reserve nearly at Happs prices or were like an original Defender door or something that I wouldn't be comfortable hacking (and I couldn't afford...). Finally E-bay in the US has come up with some good finds part wise and bits are often so cheap that by the time the big shipping bill comes in it's still cheaper than the part alone over here, but (and on to my soap box now), it really p's me off when people put themselves as shipping internationally then won't respond to requests for details from over here - I've tried this with a number of coin doors and always had no response!
Sorry about the long post - you know how easy it is to get carried away...