I have a hole in the wall which is substantially bigger than that required.
I need a round hole but don't want to line it.

If I put a tube into the wall that is smeared with a good dollop of
vaseline, then mortar round it, when the mortar has gone off, should the
tube glide out easily.

Cut the smut please this is a serious question.
--
the_constructor

Don't tip it, recycle it. Join your local group.

http://freecycle.org/display.php?reg...ited%20Kingdom