Steve Loft typed:


The branch on the soil pipe has 3 1/2 x 3 1/2 stamped on it.

There's a picture of it he
and a picture of the pan connector he

http://www.wanlockhead.org.uk/files/connector.jpg

Marley do an off-centre straight pan connector which will go over your pan
and *into* your cast-iron wastepipe, which should gain you a few inches in
height.
The more expansive option is to look around for a wc with a particularly low
outlet, infuriating at times there was no standard height for these.