Have you considered a different bike? Millions of people throughout Europe ride to/from work everyday and do so in normal clothes on normal city bikes. They consider 'kit' for anything less than 20-30 miles silly.

More: City Bikes | LocalMile

In my experience a road bike is tough with anything other than proper bibs or shorts. OTOH, I ride my Workcycles Opafiets every day to work, lunch, grocery, pharmacy, etc.