I reckon about £80 for my laggy atm. Put £20 in the other day and that gave me 1/4 of a tank. Mind you, I always fill up to the pump click, dwell a pause of two marching paces and then put about another litre in after that, so it may be more than £80.
Normally never get fuel into red, so is all a guestimate
Currently in shelster's garage: 2008 Clio 1.5 tDI Initiale