Walk if at all possible. Driving in the UK is no longer a particularly pleasant experience due to congestion and riding any sort of bike is simply too dangerous.
But if I had to bike or walk, I'd probably just walk. There's no bike racks for me to chain my bike up, so I'd just have to chain it to a pole or tree or something and hope for the best. I wish we did have some bike racks though because I would absolutely go and purchase a bike and a chain to lock it up with, and ride it to work on the days where the weather was nicer. It'd probably take me a little longer to get to work, but the extra exercise wouldn't hurt too much.
I’d probably bike as there are a lot of dedicated cycle lanes but I prefer walking but because I’m always pressed for time, cycling is the faster option.