How to repair leaks/remove pump on Ferroli Optimax HE 31C Super plus?

I had a fault code with my Ferroli Optimax HE 31C Super Plus showing it was a return sensor fault. I found that a leak from the return pipe just above the sensor had shorted it out. I bought a replacement sensor and attempted to repair the leak. I am a new gas safe registered heating enginerr so though it wouldnt be a problem.... wasnt i wrong!!! It appears that you need to take the pump out to remove this return pipe but can find how to get the pump out!!! Can anyone please give advice or help???

Helllllppppp!
January 2014