Probably a numpty question, but hey this is STW so nobody will take the pi$$… anyhow I'll be starting a new commute in a few weeks, 5 flat-ish miles to the station, then train from there. There's nowhere obvious to change so I'd prefer to wear the same stuff for commute and daytime – just wondering what folks in a similar position do when the weather's mucky? Is it just a case of slapping on some overtrousers or is there a more cunning solution?

Yep, overtrousers if it's heavy rain. Maybe just longjohns if it's cold but dry in winter.