Saniflow : Coupling copper pipe to soil stack

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 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.
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