Laser Head blanking plug

[softweigh]

Hi Guys
I REALLY need some help.
I had the usual "water in the oil" story last week on my little KA1300 Laser (1981) I pulled the head off expecting a blown head gasket but it was perfect!! However I found a little round aluminium plug and discovered that the head has an extrusion below the cam, between the first and second set of head bolts (it looks like a little volcano) and the blanking plug had blown out of it. Ford Spares say the head doesn't have a blanking plug!!!! However I found a brass cup (welsh plug I guess???) and whacked it in there and it seemed pretty tight. On re-assembly the sump filled with water !!! and there was plenty oil in the radiator too.

The head is off again and the brass cup still looks tight ..however it must be leaking.

Can anyone tell me what the correct way to fix this is????

All replies appreciated

Chris