Right so today I've stripped it down to the V and had a good poke around and I think it's a false alarm on the head gasket!
I pressure tested it, felt around the head and couldn't feel any wetness and peered down the back of the head in the gap between the dispack and it all looked dry!
But for all that I couldn't spot where it's leaking.
The HBV showed some signs of coolant around the pipes so I tightened the clips but it didn't look like it was leaking, even when I worked the valve. I ran my hand around all the pipes down the back and again all seemed dry. The coolant bridge looked OK, but the oil cooler plate looked as though it has 'weeped', but nothing like the amount that I'm losing!
I did find a leak that I didn't know about from the LPG vapouriser under the front bumper on the offside, so that's where I'm losing some of my coolant, but dosn't explain the torrent down the back.
I guess the next stage is to get some new coolant bridge washers and some goo for the oil cooler plate, drain it all down and with the coolant bridge removed I'll be able to see down the back better and reseal the oil cooler plate.
Does the stainless coolant pipe that comes out the back and goes round to the rad ever fail?
Sorry for the ramble, but I'm a bit flummoxed!
Still, happy days its not the head gasket!!