A reply from Tracbar245 sent via email:
 
 
Hi Paul,I would say when I was doing them regularly, around 2 1/2 hours was nearer  the mark, however, as it is very unlikely that anybody there has ever done one,  I would say thats a safe calculation for them.  Some bits may be a little  tight through rustIf you need any advice or parts, just send me an email, as I am a  Renault trade partner and have full access to the Renault parts database. Most  things for the R4 are readily available, Unfortunately I am not so lucky, as I  am now rebuilding a R5 Gordini (Alpine) turbo and short of a set of plug leads  and some new locks, thats about it.Regards, Chris