I really have trouble believing that this topic has warranted what almost amounts to serious discussion.
Please, all those who wish to 'dress up' before flying, have a look at yourselves in the mirror, and try to take a long, slow, reality check.
If you do happen to be at a school which requires the wearing of uniform, then you'll have to put up with the conditions of the job. Some (eg Cabair - where many of today's better airline pilots cut their teeth) have their reasons for uniforms. Others are merely glossing over the cracks.
Much PPL instruction in the UK is woeful in content and quality - getting dressed up isn't going to help, but sorting out your flying and teaching will.
And no-one looking at you in the car on your way home will think you're big or clever, either.