Help - Ground Floor Toilet Replacement (UK) - Glazed Drain - Bit Long

Hi all
I have a 1970s property which AIUI is probably one of the last in the UK to be fitted with glazed drain piping system. I am looking to replace the original downstairs WC with a more up to date model. The waste drain outlet is cast into the concrete floor approx 270mm from the wall of the room. The problem I have is that the existing toilet has a down pointing waste outlet which is mortared into the flared socket end on the drain pipe. So above floor level I have a 200mm o/dia socket which tapers down just before it enters the floor.
Without breaking up the toilet (which I understand is the accepted way to remove it) and digging out the mortared in outlet, I am not sure what is below concrete level.
The questions are:
Is the drain pipe below the socket a standard glazed swept bend type fitting? If so, does anyone have a link to dimensions for these? Can I simply cut off the socket and taper to leave the pipe flush with the concrete floor? If so how is this best achieved? Will this leave enough straight pipe below floor level to provide engagement for a plastic waste fitting? Is there a fitting to do this job i. e. go from a horizontal toilet outlet into the bore of the drain pipe that will be left after removal of the socket?
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