What's the issue you're having? Just choose a destination, plot a direct route then move it around anything you can't go through!
Seriously - Stansted and Luton are simply Class D airspace and 99% time give transits, Gatwick may be a bit more hit and miss.
Just avoid London and Heathrow itself and if you're in any doubt, remain below 2500ft to avoid all the Class A.
Nottingham to Stapleford can be done in a straight line avoiding everything - just remain below the stub at Stansted.
Nottingham to Southend is a straight line calling for Class D transit at Stansted. Seeing how Nottingham is surrounded by Class D you should be used to that airspace anyway.
Go to North Weald - it's better, with a cheaper landing fee and you'll get to see interesting aircraft!