"I am after the connector which you fit to a tank and attach a hose to the other end. In the US it is called a bulk head. What are they called in the UK and where can I find one?"
Check your thread on GW.
If you want to use hose, which may not be a good idea if it will be buried then, from the tank connector to a 1.5"BSP aquamax connector from the likes of ER koi, then to a 1.5"BSP inline hose, Oase, and that has a hosetail on the 'other' end.