I am jealous about your renaults! (just kiding)
Had same combination few years back. But R5 had to go!
As this temp sensor on cylinder head he is know get broken and start to signalizing on dashboard but actually there is no overheating.
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I can try at local renault dealer shop look for price and is it still available, and let you know!
Also!
It might not be bad idea to reconsider changing head gasket.
It is not so big job, and not so expensive.
it is old engine and gasket could start to rot.
I have changed on my 1.1 engine while doing major car rebuild, and it was rotten on one cooling channel. Not much but would start to mix water and petrol in some time.
I am not scaring you just trying to give you some info about whole problem!