I got the same kit and sewed it in to my Hein Gericke liner, it took me about three hours to do it as well, tried it out and it got a bit warm, just so much that you knew it was working so it was more of reassuring warmth than a real warmth, it could be that I didn't do it properly though I think I did a pretty good job of it, unfortunately I forgot that I had it plugged in to the bikes socket and the whole thing came to an early end at the first petrol station, bought a Stormrider instead,
http://www.exo2.co.uk/exo2.html and that I can say is absolutely fantastic.