A failed German invasion of Norway would not necessarily leave more fighters available for 11 and 12 Groups in 1940. The aircraft might instead remain deployed in Norway. Holding a new theatre creates its own air-defence, basing, and operational requirements. A counterfactual cannot simply return every historically lost or diverted unit to the most famous later battle.
Notable Point · 3:36:57-3:37:26
Why holding Norway would not simply add fighters over Britain
If Germany failed in Norway, British fighters freed from the historical campaign might remain committed there rather than automatically reinforce 11 and 12 Groups.