Would you really go through POL?
Well, it's the "standard route", but that doesn't always count for as much as the sort of practical experience that you mention. I've only done it once or twice, and IIRC though filed via POL got routed painlessly via MCT.
The point is that I would do it at higher level, not lower level.
Winds 260 at up to 55 knots much of the way down between FL50 and FL100,
What concerns you about that? Mountain waves? (Just asking -- I'm a flatlander and mountains + wind scare me.)
possibility of hitting the freezing level south of EGPH,
So stay a little lower until you get to warmer air.
and you'd have to request a non-standard IFR departure out of EGPH which they might not give you.
Why non-standard? I haven't flown it, but the SID looks like TLA at 6000.
A very long and very tiring and probably scary flight. Low level option not much better.
My instinct would be that the low level option in the boundary layer would be much more tiring.