is there a way of gaining entry to the car some other way ?
any ideas as to the cause?
Unfortunately he has just spent £8500 on a new engine (it had only done 70,000 miles) so he's not best pleased (understandably)
Your best bet is to take it to Renault - although moving it when the brakes are on won't be easy. Still your mate can be safe in the knowledge that once a massive lifting lorry (like the ones bailiffs and clampers use) has safely transported it to Renault their helpful friendly staff will already be waiting at the door rubbing their hands together with no prior notice required
Are you able to get into the bonnet at least? - If you can a possible battery disconnection might reset things... or make it worse.
Short of Renault working a miracle your only other options are really.... just one: Brute force. Hammer through window (cheapest), dynamite, can opener, crowbar... the list is endless along with the expense thanks to Renault.
£8.5k on a new engine? - Ouch!!! Most people buy salvage engines. I take it your mate actually got a brand new engine with no miles on it? Yikes
Nice.. if you can afford it! I looked into it a while back myself for our safrane as the cambelt has caused a real headache.. Renault quoted me £4k for a refurbished engine - refurbished
and they wanted the old one back in order to offer it at that price!
As for the cause of your friends locking.... That'll be Renaults overly complicated electronics. They seem to suffer a lot of niggles for some reason. The newer cars seem to be far worse than the older ones.
Good luck and keep us updated!