Well, I wouldn't cycle in my Saville Row (OK Nathan Road) finest, though I am tempted by the potential freewheeling eccentricity of cycling in tweeds. That said, I take issue that you need to buy a special uniform to ride a bike. Special uniforms are for skiing, BDSM and superheroic crime-fighting. I wouldn't strut to the shops in skin-tight leggings (even if were French, which I am not) so I'm not about to ride a bike in them. And the club tops. Holy lemon smoley, the colours can actually abrade normal people's retinas. No one should ever wear clothing where the colour scheme appears to have been devised by Rolf Harris on LSD. I shouldn't have to whisper you a confidence that your mirror will have already yelled at you through a megaphone.
In winter, trousers of suitably sturdy variety and a layers as stipulated by the weatherman are fine. In summer, shorts and a t-shirt. You'll look blissfully normal, it's cheap, comfortable, and you can change into something more formal as required by evil corporate overlords.