1997 1.6 petrol coolant leaking after thermostat change

Hi all,

after finally managing to remove the bolts holding the thermostat in place i replaced the thermostat and o-ring. (thermostat in first then the o-ring snugly over the top) i then tightened the bolts back up and topped up the coolant. Straight away i could hear water dripping underneath the car... had a look and coolant is literally pouring out. the coolant is dripping from the bottom of the oil sump so i assume it is coming from just above that. However i cant see any liquid near the thermostat housing which i just reattached, it seems to be coming from behind the housing underneath the inlet manifold. It was fine before so must be something i have done I undid the bolts, checked the thermostat and o-ring and reattached. Same problem. Am i just being rubbish at keeping the o-ring in place when i tighten the bolts or have i perhaps cracked the housing??
I dont think i can bring myself to do anything else with the thermostat housing (my hands are shredded from squeezing in that tight space) so am thinking about towing the car up to my local garage.
Any advice or thoughts would be much appreciated though!
Cheers!

Thanks Jenno, I'll definitely give that a go... just checking should i put the thermostat in the housing first, then the o-ring then bolt the pipe on? Or put the o-ring in the pipe then put the thermostat in the pipe over the o-ring and then attach the pipe to the housing? if that makes sense...