One can in fact learn to fly at an unlicenced aerodrome, if one chooses microlights. They have two seats, can be 3-axis, high-performance, MTOM 450kg (I think), and require exactly the same skills to be learned as those for an "aeroplane". These unlicenced fields require no fire crew, runway "slopes", no 2 metre x 2 metre yellow "C", etc etc.
Not only is an unlicensed aerodrome not required, but the instructor, who may receive remuneration, does not require a commercial license.
But if one wishes to learn to fly an aircraft with MTOM 451kg, the rules are quite onerously changed (under current legislation).
I would suggest that any training up to PPL standard could be conducted at "approved" airfields [approved perhaps by organisations like the BMAA]. Any training thenceforth towards any "professional" licence would need to be conducted under circumstances appropriate to the type of professional licence being sought.