I'd say part of the answer would be in the question "What is the purpose of the trip?".
However, I used to do the run almost every weekend....Whitegate, Lichfield, Daventry, Lambourne, Brookmans Park, Detling, Dover, "Point Charlie" (on the FIR boundary), Koksy, turned left direct Oostend.
I know you said L2K, but we always found EBOS to be better/cheaper for what we needed/wanted (IMC rating training). I'd consider the same route, but with a right turn at KOK for L2K.
Forgive me if I got any of those in the wrong order - not flown it for some 16 years and was working from memory (no map to look at).
Always took us 3 hours in a PA28 (each way).
BTW - was discussing just last night - can a trip like this still be VAT free and claim fuel drawback?