So Ive looked at the RR today and changed both Heater Valves and as predicted heater is no better still at best luke warm. Temp gauuge only goes up to below quarter. So I assume its the Thermoatstat.
Ive looked at the post re changing and it does look a pig of a job, was thinking though would it be easier to remove the front panel headlighyts rad etc and move everything forward to gain access .

Thanks

Or the Renault 5 thermostat mod ...

https://www.fullfatrr.com/forum/topic57532.html