Do consider a drop bar bike, I use a Boardman CX, disc brakes for when it’s wet and can also get used for other things at the weekend. Mudguards are handy
I’ve fitted a rack (can be removed in seconds) and use a Carradice Bike Bureau that I got cheap on ebay. Bombproof, holds an amazing amount of stuff and looks fine off the bike as well for the days I drive
As others have said, leave lock at work
Why no lycra? I’m old and fat but still wear it, it’s just more convenient. I’ve a selection of long and short sleeve base layers, fleeces and a soft shell jacket that can be combined as conditions dictate. If it’s properly raining I either drive or accept that I’m going to get wet either from above or from sweat. Haven’t found a cheap waterproof yet that’s breathable
Shoes are ok in the summer but a pair of winter boots makes all the difference when it’s cold and wet