I've been thinking about buying some lenses for my iPhone and I like the ease of use of the 'Olloclip' attachable lenses. I'm looking at some on eBay which look exactly the same as the official 'Olloclips' but are a lot cheaper - I was wondering whether anybody had tried any of these cheaper models - presumably the glass is inferior but I wondered if it was still useable? I know you get what you pay for and all that, but Olloclips are like £60 in the Apple store.....