It's similar here - I leave pretty much when my timer clicks over 8 hours (don't take a lunch hour - 20 minutes tops if Tesco is busy) and people are definitely glaring at me.
At one job we had set hours 8:30 to 5:00, I was ALWAYS the first one out; packed and walking at 5:00:00. It became a joke, my line was, I'm the first to leave so no one else would suffer the stigma, taking the hit for the team. Our manager was not pleased, but my work quality was good, so he lightened up after a while. That company later tanked by the way, entire IT staff was laid off. I had left for greener pastures long before.