On shipyards, there's a simpler solution: Until 1940, Airspeed was associated with Swan, Hunter and Wigham Richardson - SC Swan and the Wigham Richardsons (George and Philip) being Airspeed Directors. So, a simple what-if: Swan, Hunter refuses de Havilland's 1940 offer to buy all of its Airspeed shares. There, that's DH out of the mix 
Cobham does make sense though (Sir Allan being one of Airspeed's most ardent supporters). Maybe reinforce the connection to create opportunities with Flight Refuelling Limited. Perhaps a dedicated 1950s RAF air-air-refuelling aircraft from Airspeed/FRL?
On the design front, an easy what-if would be having Hessell Tiltman stay at Airspeed as chief designer. He was a parter in Tiltman Langley Laboratories since 1938 in any case (obviously, Airspeed had no problem with him 'moonlighting'). So, was Tiltman bored with Airspeed or did he just move fulltime to Tiltman Langley Ltd to push the Gerritsen Gear?
If the latter, maybe make JJ Gerritsen TLL's Technical Director while Tiltman keeps designing planes for Airspeed? If the former, perhaps hire Marcus Langley as another designer for Airspeed (his BA Eagle experience might have proved useful if Airspeed chose to develop smaller civil aircraft types). And, maybe, Tiltman just got on better with Langley than with Norway?).
