Did your "plumber" check the joist?.
Cut the cast as near to the branch as you can and use of of these,
Pushfit waste has always been a smaller Diameter than ABS.
In comparison with the earth clamps that's 1/2" copper in the pics.
Probably be silicone.
Did you unscrew the centre first.
Have you tried the old nut on the new trap?.
No need for a washer, there's a taper on the bottom of the overflow that makes the seal.
Shut the water off flush and empty the cistern, loosen off the overflow stand pipe back nut and you will get the play you need.
Evidence is beginning to show the proportion of smokers infected with coronavirus is much lower than the rates in the general population....
That looks like a 1/2" Female Iron x CU Straight at the wall, remove the hex from the back of the old tap and the new tap will screw into that,...
Remove the "O" ring and solder over the flat end refit the "O" ring and you have a plug.
If it has to be swept and non ferrous, 2 x 45 deg bends joined with hex nipple and the other for your bsp paralell thread you need for the...
Cut the soil pipe back and fit your black bend into the spigot of one of these, you may need to cut it down a bit.
1/2" Alkathene is 21.5 mm OD, a 22mm compression elbow will do with 3/4" olives .
About 15 inches will be plenty,
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