The heater matrix in my Berlingo van sprang a leak a few months back. It's dead easy to replace the matrix - all you have to do is remove the
complete dashboard and it just unbolts...! As an alternative, my local garage sold me some of this stuff:
http://www.autokits.co.uk/forte-radi...leak-p-42.html
...which sorted it out in a couple of miles. It's still fine. I realise it's not supposed to be a permanent repair, but it saved me several hundred quid for labour alone, so I thought it worth the risk.
I have to agree with the sentiments being expressed here though. If you can manage to hang on and get a new rad fitted, it will clearly be better.