Its illegal in the UK, but pretty easy to get weed, and pretty much most people I know have/do smoke weed.
To be fair though, you do smoke cannabis, so chances are you're friends with people who also smoke cannabis, since it's in large part a social drug. I don't know of anyone who smokes it, but doesn't have any friends who also smoke it.
You can certainly get ahold of it in most towns, as there's usually some dealer somewhere, but I don't think consumption is overly common, as it goes.
Anecdotally, I've got entire groups of friends where none of them smoke, or even have smoked cannabis.
But there was always a small group at school, sixth form and now uni who do.
