Hi mr-reno-139 thanks for the help. I have managed to get one and fitted it yesterday. It was a bit fiddly but between two of us we got it on and the difference, just pressing the clutch, is amazing. The engine mount looked pretty new and is in good condition fortunately. Putting a new battery in this morning then for a test drive!
Luckily Renault 4's are very popular here in Portugal - I believe they were actually manufactured here back in the day - so the availability of spares is quite good. There are some real beauties too. I hope to have mine restored to a good standard by the summer.
I still can't belaive someone had taken the bracket off and not replaced it.... The juddering was horrendeous! Mind you, they way they drive over here it's not entirely surprising