I had a new boiler installed 6 months ago along with 2 new raditors . When I turn the heating on/off I get banging of the pipes in 1 particular part of the house . I have bleed the old raditor to which the banging is close to but still banging noise sometimes quite loud.

Steam boiler I presume?

No combe

If any new piping was installed with the boiler, cutting oil may have been introduced into the system. This could also be due to binding of the pipes against the structure. Expansion & contraction will occur as the pipes heat up & cool down.