Ade,
How about M1 then, I would join M1 via M45, so Watford Gap Services would be the obvious choice, as only a minute or two after M45.
Grzegorz is riding back with friends from his RAT pack, so I can come back up M40 and see a friend at Haddingham, which would split the journey nicely in two for me.
Will emial John and see if he is still going with his lad.