On Aug 15, 9:23 am, Mr Uncalled-For
wrote:
I have a 3 1/2 inch drainpipe that I need to T into

Well, I checked with a plumber and apparently I would:
* Not be permitted by 'building control' to use the strap-on-boss
solution.
* Would have to do it all in cast iron (externally, that is).
* Have to get a building warrant, covering the entire job, including
routing of the pipe internally.

So, from previous rough quotes I've had in the past for putting
together building warrant applications, I bet it would probably all
cost in the region of £600 if I'm lucky.

For installing a kitchen sink!

But at least I'll now have various speedfit fittings and plastic pipe
that I can take out admire of an evening.