Why not contact who ever is making the monocouche render for advice on a pre-rend on concrete? For example Weber :RpS_cursing: would advise their rendaid as a base, K Rend would probably advise HPX etc. Then if anything goes wrong you can contact the manufacturer but don't bother if it's Weber cause it will end up being your fault so save yourself the embarrassment.
Yep i will certainly do that , just thought i would ask the experts who actually use the stuff for some advice and hopefully get a quote to do the works , had 2 pm,s so thanks to them