I park on the backstreet behind what used to be Ruskin Hall. Never have any issues to be fair not exactly M6 friendly though.
You can get straight onto the expressway from there and then onto jcn6 dead easy. Used to use Ruskin Hall years ago. They had a Celtic supporters club there, and I was once threatened by an enormous fat bloke with some kind of IRA retribution because I called him a fat bastard for knocking 3 pints out of my hand with his giant belly, lol