Just bought a house with one of those huge leylandii-type triffid things
(just one) planted outside the front door. Surveyor mentioned it as a
'caution', and no damage to the house is evident, but I defintely want rid
of it. The beast's trunk is about 4-5" diameter at the base; it reaches up
to the guttering (1st floor, so about 17' tall?) and is only about 18" from
the front wall of the house.

I believe that simply chopping it down could cause more harm than good, ie
if there are roots under the property which then rot away leaving voids...
can anyone advise what I should do? Chop it down in stages? If so, by how
much? and over what period?

Thanks
David