[RTuesday]

Does this mean that their "real world operator" is Manx Teleceom, like FL1 for Riiing?

For roaming agreement purposes, yes. The incoming numbers are within a Manx Telecom range, but have been subcontracted to a local company who provide various phone services (callback etc) who have allocated a range to gt-sim.

Their site 26cent.de is interesting though slightly less informative than you'd hope

You're not kidding - you have to know what the product is before you can work out what's going on. They say they don't get many customers using Firefox - it's easy to see why... Even with MSIE it's a bit flash-heavy. I agree not the cheapest in most places, especially when you take the cost of the SMS into account, just another call back service.

But the reason the SIM is interesting for me is that it has a local (to me, and many family and friends) mobile number, and does roam on the island so I can test it here (unlike Riiing and Hop).