Very cool. 250 quid is steep, but I assume it's a one-time fee. For those really considering it, I'd suggest you wait until a bit of a longer term study is done before attaching something like this, permanently, to your body. Even if just because it might screw with your ability to get an MRI or CAT scan in the future.
I have always wondered what it'd be like to have that perfect intuitive sense of direction, but this is something I'll pass on for the time being.