Hi, I’m putting in a new radiator and have been completely flummoxed by the old microbore central heating. The valve union where the radiator tail connects appears to be 1 1/4 inches (although the brass cap I bought from screwfix has 3/4 stamped into it) weird. The new radiator tail has a 1/2 inch thread (I didn’t know to remove the old tails which would probably have been too big for the new one anyway and have dumped the old radiator). There doesn’t appear to be such a thing as 1/2 inch tail to 1 1/4 valve union which also needs to be an extender of 3cm each side as the old Rad was 65cm and the new one is 59cm. I really don’t want to drain the whole system or replace both valves if at all possible. One option would be to fit the 1/2 inch tails I have (3cm long) and drill a 10mm hole in the 1 1/4 brass cap which fits the union and join that end with an olive. I’d that doable?