Took it up to Vx and had a quiet word with the Techie. Ran the Tech2 over it and fault code still PO100 - MAF sensor - but he did search for software updates and installed newer version 2.096 for me.
Turned off the engine and fired it up - oh shitt - it rumbled like it was missing a cylinder (and it's already 2 down) and the EML lit up - Zero throttle response.
Knocked it off and on again and we're in business - Throttle whizzing up and down like it should and idle consumption now constant at 0.2 (ususally 03/0.4) - Hoo bloody ray
MAF fault still present and lit up again on the way home, so I'm gonna fit a new MAF £40 on Ebay (genuine Vx & new) and he refused my bung for the second time - so actually it seems fair enough to me. He seems to know his Meega's and says they shoudn't but do fail often - I know this isn't always true but it's worth a go at this stage.
I knew I hadn't buggered it up myself
What's next - Fuel Filter tomorrow and Wishbones next week