Did you manage to solve this at all?thanks both, appreciate the suggestions. Have managed to find someone to have a look at it tomorrow so hopefully they will be able to help on the day.
Think it is foxes. I have bought a couple of ultra sonic things they are meant to hate and some spray. Bloody pain! the repair to my mini was £300 already this week (not to mention 2 new tyres and brake service on top)!
I've been done by foxes today - chewed through a NOX sensor and some other bits. VW Assist bloke is repairing at side of road and smearing with grease / chilli powder - but wondering if anyone has any other success stories to stop it happening again.