Yep I usually buy from Morrisons. Never have any problems at all. Considering the fact they bunker out of Immingham like all the shell/bp etc stations in the area don't see the problem.
Only Shell V-Power goes in mine. If you buy shell V-Power (wot Optimax is now) that comes from a single dedicated production plant, rather than the pooled petrol that regular ones use - according to EVO's recent article on petrol.