I'm not British and even though I've been living here for the past 12 years, but have no British friends, so I have no one to ask to. My DP is useless in this way and keeps changing his tune. I've always planned to invite some of my colleagues. They're nice people, but I wouldn't call them my friends. I've only hung out with them a couple of times and well I haven't seen them in the flesh for 15 months now!
I'd only invite my bosses to the ceremony (it's traditional where I was born) and the HR lady as she's keen to learn about other religions and it's a Jewish wedding.
Originally I was planning to invite some mums from school but I'm sure that by the time the wedding comes I wouldn't have spoken to them in years.
It's all a real mystery to me anyways, where I come from you invite as many as you can and there isn't such a thing as ceremony, wedding breakfast and evening reception. If you're invited you're invited to all of them.