Peter coughed up some electrons that declared:

I am about to connect 4 inch waste from a new attic conversion to an
external cast iron one. Currently it rises to above roof level. Some
questions:-

As my angle grinder wont cut thro 4 inches should I cut twice ie make a
sort of inspection hole and hacksaw the back or is there an easier way.
(for direct connection at attic floor level)
Should I replace all to ground level or to existing 1st floor
connections.
Will new plastic fit inside old cast iron joints.

Many thanks

Peter

Could you get one of these in?

http://www.hss.com/g/68230/Soil-Pipe...-150mm-6-.html