You may as well just use 75w-80 transmission oil, it's even the standard on a Renaultsport model. I don't know the ins and outs of uprating this, but I'd say it's probably a waste of money to do this in the UK for a standard road car.
Elf Evolution SXR 5W40 is a Renault recommended engine oil, it's what many people on here put in their cars. If 5W40 synthetic is a recommended grade for your car, then I'd go with that one if you wanted to put some reasonably priced good stuff in.