Cheers guys. There are now 2 solicitors dealing with this, one for the hire car, one for the accident damage. Both have confirmed I'm just a witness, no need for a solicitor, no need to worry about costing me in legal fees. FEW!
Neil, the chap who hit our car even got out of his car, gave my wife contact details (inc phone number), apologised and said he was shocked, too.
Then the insurance contacted me some months later to say he is saying he didn't hit our car and that he only got out of his to see why my wife was walking towards his car.
Lying through his teeth, guessing because there was no damage to his car and he didn't fancy paying his excess and losing no claims to fix someone else's car :-(
Had I known he would lie, I prob would have got the damage fixed myself rather than risk my no claims/excess.