As it's a new house maybe the walls are built of Thermalite or Celcon
blocks.
If so they're so soft you can almost do it with your finger nails. I'd
have a
go with a hammer & chisel first before buying expensive gear.

Peter


Ah no - the house is new to me, not a new house. Its a 50s ex-council job
and the walls are VERY solid - mainly solid brick (don't know exact type
TBH) or stone in places.