Having done a similar route recently, from Turweston, over SilverStone (watch for their heli pleasure flights), to Cranfield, asking for a zone transit, then towards Duxford. Check NOTAMs to see if Old Warden are active, and make blind calls before going through their zone, as they may have traffic even if the tower isn't manned.
You can go under the Luton zone edges (below 2500, 3500 or 4500' depending on where you are).
I'm based at Halton so know the area quite well.