In terms of straightforward performance, there were various comparitive trials conducted by the Royal Aircraft Establishment (RAE) and the Aeroplane and Armoument Experimental Establishment (A & AEE) during the war. The results of these are widely published in the better books on the individual aircraft types.

Some of the A & AEE trials, as well as those of the AFDU, pitted two aircraft in a ‘combat situation’ to enable tactics to emerge (though this tended to happen towards the end of the war, not at the time of the BoB)

An example of some of the results, in this case 109E v Spitfire I, is at http://www.spitfireperformance.com/spit1vrs109e.html

An AFDU report from later on is at http://www.kurfurst.org/Tactical_trials/109F2_UK/109F2_ES906_AFDU.html

Hope this helps!