Finally got the chance to take the fatty out for its first proper run since I bought it tonight..i have now noticed when I select drive or reverse the lights and interior lighting slighty dims and the car will rev at the very same time? I got the meter out and batteries 11.6 and 14.1 with the engine running..could it be the batterie affecting this? Apart from that I've fell in love with the big brute.. Pcv valves getting replaced in Saturday so I'm going to fit a new batterie at the same time and hopefully rectify this issue....

My first checks would be the battery and alternator.

Really tired at the moment, but I did have a problem on my P38 where the lights would 'fluctuate' and constantly dim up and down. Turns out the rectifier was knackered on the alternator, £20 and half hour of my time and it was fixed. Not sure if your problem is similar but at least you know for the future  

Thanks for the heads up.. Will check that out first...

P38 alternator maybe cheap and easy to get to but l322 alternator will be a far bigger price