I don't have any experience with uprated clutch on the clio but have a question. What power are you running and how many miles? I noticed mine slips just like your clutch when I was at Spa with 4k miles on the clock.
My tuner has installed a Helix reinforced system on mine. Works fine for me.
If you're interested, I still have a Helix reinforced clutch plate and standard (LuK) pressure plate for the Clio III RS...
Here's a pic
Reinforced plate has done less than 1500km, pressure plate about 30000km on a standard car. So both in very good shape.
More info: PM me.