....have a look at my post in the Sherburn PIREP thread, re. our trip up from Wycombe.
We delayed leaving Wycombe until approx 1130L. Were able to get to 2000' QNH initially, but the worst of it for us was probably between WCO and DTY - had us down to 1600'-1700' to remain VMC for most of that leg. Vis underneath was ok, but not great (Turweston available as a bolt-hole incase it closed in further).
To the N of DTY, there was a marked improvement, pretty much CAVOK by the time we passed abeam East Mids.