I have a similar problem, although I have to couple a copper pipe from
a Saniflow to the cast iron pipe and cannot get a strap around the
pipe...

So, does anyone know how you would go about coupling a 22mm (or
possibly
32mm if my route is 12m - touch and go) copper waste pipe from a
Saniflow to an old cast iron soil stack. As it stands I would have to
drill a suitable hole in the stack, then couple it some how. This is
the bit I'm unsure about.

The only complication is that I only have access to one 'side' of the
stack. There has been an extension on the house and the soil pipe now
runs down partially behind the wall of the extension:

house
_____________
house wall ______|O ---soil stack (I can get to this side of it)
-
|
extension |
|
|

My rudimentary diagram does not show that the 3 walls that surround
the stack are very tight against it and all cemmented up to the pipe,
so I don't think I could get any strap type fitting round the pipe.

Really appreciate any advise on this. Thanks in advance.