you can buy a replacement one in two halves so it's easier to fit as they're a bugger to get in and out, can't remember who does them but someone will
i'm doing my ordering as we speak, I could really do with getting these at the same time to save on the postage and all that but cant seem to find em
http://www.alanhschofield.com/ourparts/prod_2687545-Heater-Tube-YPiece-7279-211255755D.html ££££££££££££££££