Free Frame!

So... I just got myself a free IRO Mark V frame that Cavendish were gonna throw out. I think it's a Mark V anyway...
It has a crack in the headtube, but I think I might be able to repair it with this stuff. It's a special kind of braze that you can use on aluminium without any special kit. If it actually does what it says on the tin, then I think it'll be fairly easy to fix!
So my questions are...
Has anyone used this stuff before?
Does it work?
Does anyone have a suitable (hot enough) blow torch I could borrow to test it out?

errr, mark v is steel mate.