I'm now convinced I've found the 3/4 fill problem.
and I'm not too happy about it.
Tonight I've been to a different garage and topped up again until the pump stopped, after this with a very slow rate of progress I wiggled and giggled the nozzle until petrol suddenly started pouring from the tank.
I got back in the car and started the engine the petrol gauge still only said 3/4 full.
My conclusion now is its either the sender or the petrol gauge thats defective. Altho its no major biggy, and I also know that Renault will sort it, but I dunno if its me expecting perfection, but I feel this is no way to enhance the sales of a brand new car 2 days old. Renault will be getting it in the neck again from me.