Thanks guys. Think Scream may have hit bulls eye. I generaly hear good things about Vallejo paints. Perhaps this'll be the time to break the GW habit..?
Would still be interested if anyone has good or bad feed back on GW's Lahmian Medium ? (Yep i know Vallejo do their own medium too - but GW is just too easy as i pass the shop every day

) Hoped it might save some of my old and crusty pots as well as provide all the washes i could ever need...
Wondered if the problem might be that i'm trying to wash straight over primer (Halfords white) ? (though i haven't noticed much problem over grey with GW Flesh Wash.) As this is the basis of the army painter system i guess it should be fine? The watered down black i've tried looks fine when wet but then actually seems to leach out of the reassesses as it dries and leaves just dirty tidemarks everywhere. Seemed to get away with it on my falcons (ToEG) but looked crap on my jet bikes. Had to do it all by hand in the end. As i'm about to launch into all my aspects in white i was wondering if i should reconsider. Anyone else had similar problems ?
Blip