Thanks for the replies regarding the water butt tap.

My fears were unfounded, opened tap this morning and water gushed out.

I have had to replace taps on other butts in the past by crawling into them
on the back garden, making a complete fool of myself ,no doubt to the
amusement of my neighbours.

This past Summer I broke a butt tap and in a panic bought another water butt
same day.the old one is at the end of the garden upturned resembling a
dalek.

Someone has suggested using a gripper stick to hold/turn the nut inside the
butt I might try this suggestion on the dalek.

Michael