I got a 20 mhz powered crystal oscilator today and it's sorted all the problems. Didn't try the other solution 'cause I took a few days off (really was having a **** time of it and needed a wee break) and waited for the crystal from "RS Components" to come. Been reading on the web that apparently it provides a much stronger timing signal and so far that seems correct (well I've got that f*cking light blinking anyway!)

Cheers
Mark