The idea that middle class professions don't benefit from collective bargaining is absolutely ludicrous. Doctors in the UK benefit massively from the British Medical Association, not just with collectively bargaining wages with the NHS, but also in lobbying for better conditions, shorter hours, and against privatisation. The ACA and ACCA accrediations are nothing but a bunch of hoops that bean counters go through in order to secure privileged access to higher wages conferred by "chartered accountant" status -- in reality, the vast majority of accountants do not need these qualifications and could easily get away with on the job training. Indeed, the vast majority of young accountants, who do most of the heavy lifting, are "part qualified", meaning they've done one or two exams and are just learning on the job; full qualification is completely unnecessary to perform the work of an accountant. The higher wages commanded by "Chartered Accountant" status is merely a grand collective bargain organised by the accountants' professional associations. The same is true in law with its Law Society, its rules against unlicenced practitioners, its lobbying to keep run-of-the-mill legal practices such a will writing, conveyancing and other boilerplate legal stuff in the hands of overpaid professionals (even though those things don't require lawyers), etc etc. Engineers have their own professional associations, as do Teachers (the unions are strong with this one!), nurses, etc etc etc.
The idea that the middle class don't benefit from collective bargaining is laughable, being as there are countless professional associations that exist in large part to lobby employers for higher wages, to restrict the supply of labour, and to make labour market conditions favourable. Professional associations are the labour unions of the middle class.