I think it would be fair to say that if the lookout had been different in either aeroplane the iincident may not have happened.
If it was runway 20 with a left hand pattern in use I would be interested to learn from any 'Shoreham-ites' on here a couple of points.
Firstly the Shoreham Airport website has a picture of the preferred tracks of the circuit patterns. How close to these are the pilots supposed to adhere? (There must be a bit of leeway)
Secondly, runway 20L has a noise abatement right turn after take off until reaching the coast. How rigidly is this enforced? Are there any shortcuts?