Got lucky with the foreman in my two cases, we all voted and the guy we elected turned out to have been a colonel in the Army and had been on court martials (presumably from the judging side although we didn't ask). I quite enjoyed the whole experience.
It's worth doing. I did mine about 4 years ago and got two cases one of 3 days at Lewes and one of 2 at Brighton. We had a an ex tank commander as the foreman and an ex member of The Cure on the Jury!! Pot luck if you get called.