Well, its accepted that the Mosquito could have been brought into service much earlier, once its concept was accepted; as it was De Havilland's had to develop it initially as a private venture. Given a diferent concept of tactical and stretegic air warfare, I don't see any reason why an earlier Hornet could not have been in service, maybe ahead of the Mosquito. To this end I would initially utilise the spare Kestel manufacturing to get the type airborne and in service, this would be a lighter version, but still superior to any opposing types. The Whirlwind would not be built, instead a Peregrine engined Hornet, then the better Merlin engined version. If the vast indusrtrial capacity was diverted inpart away from building heavy bombers both the Hornet and Mosquito could have been in service when the RAF was the only branch of the armed forces that the British could have used to oppose Nazi occupied Europe. A powerful tactical airforce equipped with both types would have been potent in attacking high value targets. Ahead of the Mustang the Hornet could have provided a decisive long range escort to the B-17's when they began to deploy; heck, they could have also done the same with daylight attacks with Lancasters and Halifaxes.
This is all 'blue sky thinking'
And lets not forget, Whittle had the jet engined aircraft ready to be developed before the war!