simple question

had a double sink
now got a single sink
the pipes were blocked off
now they are cloging up
just want to change one pipe
but can't
no one will sell the elbow i want on it's own
can anyone help?



the pipe on the right is connected
the ones on the left and the middle are blocked off
all i need is an elbow from the right hand pipe to the u-bend, but all the ones i can find singularly have the bigger fitting/thread on them even though they are all labeled 40mm

apparently i need a 32mm kit, but no one does it other than in a kit, and i don't want to fork out £20 odd for a kit when the elbows can be had for £2 (albit it the wrong ones )

where can i go to find one?