The law covering this (Occupier's Liability Act) dates back to 1984, so it's hardly a recent "namby-pamby society" issue though, is it?
https://www.protectingyourself.co.uk/using-barbed-wire-glass-intruder-prevention-methods.html
Also:
"The Criminal Justice Act 2003 provides some protection to householders. If a trespasser suffers an injury during the course of a crime, for which he is subsequently convicted and for which he could be sent to prison, he will only be able to sue the householder if he gets the court’s permission to do so. The court is unlikely to grant permission unless the householder had taken grossly excessive steps or had not been acting to defend himself, his family or his property from an offence."