Sealing central heating leak

I had a thread earlier about a leak under ground in my central heating, i was told there was a product you can get to put into the system that will seal the leak. I presume like the egg in the car radiator.
Does anyone know the name of this product and know where I can get it?

I think you'd be better off getting the leak fixed properly. I presume its something like radweld that you can use in a car radiator, which is fine for a while but the leaks usually come back. I'm sure any good plumbers merchants will have the stuff if you want to go with that method.

Fernox is the name of the most popular product for this type of thing see link

nice 1, i'll give it a go........