Imagine being a self-employed juror involved in a long trial, it could drive your business into the ground. It's one thing doing your civic duty, but...
They're also pretty good about keeping you informed as to whether you need to turn up or not. Unless you're actually on a case, or if they're doing legal arguments or something, you might get sent home for the afternoon, or you might get a text late afternoon telling you that you don't need to...
Unless it's changed much for B&H in the past couple of years, you don't get scheduled in advance to be a juror on an individual case. You get called up as part of a pool of thirty or so jurors to cover a ten day period. Then, when you get there, they draw numbers out of a hat to decide who sits...
Do the call-up papers not advise on where best to park? When I got my juror pack a couple of years back, it contained quite extensive info on how to get to Brighton/Hove courts. Pretty sure parking advice was included