Land Rover Repair: Heater core, heater core, o rings

Question
Hi John, I own a 2003 TD5 series II auto and purchased it secondhand in Dec' 2005.  I use the vehicle to tow a 16 foot caravan.  Recently, 8 weeks ago, I had to replace the heater core at significant cost $800 (Australian).  I've returned from another trip away and found that the new heater core is now leaking too.  I replaced the thermostat not long after purchase as it seemed to be sticking upon opening up.  The replacement did the same and i thought that this must be common.  The vehicle goes back to the workshop tomorrow.  It takes forever to dry the carpet out!  Any ideas?  Kind regards

Answer
I have never once replaced a heater core and had the replacement go bad, too.  And I have hardly ever changed the cores at all in vehicles like yours.  It's the pipes and o-rings that leak, not the cores.

We've certainly had our share of bad thermostat, though