Thermostat housing

Does anyone know where in Glasgow or online, I would get a thermostat housing O-ring for a 2002 Skoda Fabia 1.4 MPi without having to buy the thermostat also. The size of the o-ring is 30mm x 3.5mm.

My son has had numerous coolant problems since buying the car 2 weeks ago. So far I've fitted a new thermostat (there wasn't one in the housing?), a thermoswitch for the cooling fan (one of the three pins was broken) now the car doesn't overheat and the coolant temperature switch on top of the thermostat. He was still loosing coolant but thought it was still overheating and coming out of the expansion tank. Discovered it was coming from just below the thermostat housing. Previous owner must have had similar problems because there seems to be sealant between the housing and the cyl head! Do you need to use sealant and 0-ring to seal the housing?