Thanks Traumflug, I should have put a more specific link, [
www.reprap.org].
Yep, that component would do the job, I've also found the equivalent 5.6ohm 5W resistor on Farnell. I must have been half asleep the first time I searched!
Both ones we've found seem longer and thinner than the UB5C-5.6-ND, but I suppose I can machine the Jhead nozzle to fit =)