The thermostat kit should have contained one cycling stat and a one shot stat (fuse) they both look the same except for the colour of the dot on them, if you pressed the one shot stat in when you fitted it you have blown the stat and it will need replacing,(The opposite side to were the wires go should be slightly bowed outward), If they are ok you will have to do a continuity test from the heater back to the timer and if that checks out ok replace the timer.
casper......www.selfix-uk.co.uk, October 2008