Yes, in the UK you can do that, if disappearing into Class G. Once outside the ATZ they don't care what happens to you.
There are various nooks and crannies in this stuff. I am sure you could fly from Southampton to Bournemouth at FL50 (so remaining within a shared chunk of Class D) but that would work because the two units work closely together.
I don't think you could do an ad hoc (no IFR flight plan filed) departure from say Bournemouth to Manchester, FL100. Maybe one can? Bournemouth would be entitled to say they haven't got a flight plan so hard luck!
However if already airborne, you could - at a stretch - convert a VFR flight into an IFR clearance and continue IFR in Class A for another 100 miles. I don't know the exact process for this; I guess somebody in ATC would have to knock up a basic route for you and type it in so that London Control can see a route on their computer.
Also, in the UK, you can depart "VFR" into OVC002
if the airport does not have any published VFR minima, and I think most OCAS (but with ATC) airports don't have these.