I recently received a comment from a new reader to this blog about what to wear when raining. I will endeavour to share what I do, in the hope that it helps others. (I can be selfless you know).
I have an office in which I can not only store my beloved Brompton bikes but can change privately if required. I have to wear a jacket and tie every day to work - pretty formal stuff. I keep several pairs of shoes at work and change into them when I get there.
If it is raining I have a waterproof jacket and waterproof over trousers (both by Altura) which serve me very well as I can wear everything but my jacket (which you guessed, I keep several in my office) underneath. I rarely arrive dishevelled and it takes only a few minutes to change.
When going home, if the wet weather gears needs to go on, it does. If not, it goes straight into the S or C bag.