Correct me if I'm wrong, but your top hose would not be hot if the thermostat wasn't operating properly. Could it be blockage in the radiator?

Adi

When the cap was off there wasn't enough time for the fans to come on because coolant started flowing over the top of the header tank.
When the cap was on, the fans kicked in then.

If there is a blockage in the radiator, surely it'd have to be pretty severe blockage to hold so much pressure i would have thought. I guess pulling it out, and checking by putting a hose in one end would identify it though.

Sorry to sound like a fool, but what part is the heater tap?

If I haven't burped it properly, would taking off the cap again, and leave it running for a while help that?
Really thought I had fixed all my problems once it was in and not leaking. Haha always the way though.

the top hose would still get hot if the thermostat was put in backwards, when the thermostat opens and the coolant from the bottom of the rad flows into the engine, hot coolant rises so the top hose will get hot from the coolant trying to get out of the engine

Seems like some other guys had problems with overheating because the thermostat wasn't installed properly

Adi

I don't see how I could put the thermostat in backwards...The only thing it could do when it was out was spin around on its little metal housing (which looks kind of like a mini turbo , it didn't spin very easily, hopefully it's meant to do that??)
I didn't remove it from it's little metal housing. I just unbolted the whole thing from the engine and had a look at it then.

I think you guys with the airlock theory were right!!
My driveway is at an angle, with the drivers door facing down. Maybe some air was trapped just before the thermostat on the passenger side.
So when I waited for it to cool, I squeezed all the hoses good and proper, and a few bubbles came out. Went for a quick spin around the block, came back and there were bubbles making their way out of the reservoir top up thingo. Went for another drive/little bit of a thrash and the temp didn't go a mm higher than normal!
Hopefully it is problem solved. A longer drive tomorrow will find out for sure.

Thank you guys so much for all the advice and tips. I'd still be scratching my head at the leak if it wasn't for the help!!!