Can you believe it. I just called Dell on the number provided and the guy walked me through a set of tests. None really worked until he got me to take out the battery, hold the power button down for half a minute, then power back on. The display fired up and away we went from there. Did diagnostics to check everything etc and it all seems fine now.
Apparently i got lucky - but he thought it's something to do with residual power in the components which caused the problem.