Hello Marc,welcome to the forum.
Sounds like your friend hasn't had much luck recently!.
I'm not 100% sure,but I suspect there is a primary Diesel pump in the fuel tank which sounds as though it's packed up.I have never chnaged on a Renault before,but I have changed loads on Peugeot HDi's and Rover 75 Diesels.I would wait for a response from one of our Renault Techs to confirm the primary pump location,though....
Incidently,the glow plug light doubles as the engine management light which comes on when the
detects a fault.In certain circumstances it also goes into 'limp mode'(revs limited to 3000rpm),and it sounds like this is what happened previously.
It might be worth having the
codes read,if at all possible.This will help confirm the current problem is the primary pump,and might also show up the cause of the previous faults.See if there is a mobile mechanic in your area with the equipment needed as this would be cheaper than having to trailer the car to a garage.
Edit;Just a thought,but does the immobiliser light flash when you crank the engine over?.The manufacturer immobiliser(controlled by a chip in the key) cuts the fuel pump(I think....),so this might be faulty.Have you got a spare key to try?.