To find this micro cache, you'll need to own, see, find or otherwise have information from an Aluminium Alpha Numeric Disc (aka AAND), the colour of which there is a clue to on this page. The cache is hidden at N51° 4A.CGB W 000° 5F.EBD.
Alternative finding method, as required by Groundspeak:
(This is a lot less fun than tracking down one of the hundreds of this colour item released into UK caches and at events in the summer of 2012, but as a last resort..!)
A is even, and greater than C
B is neither even, nor a prime
C is the number of seals in a film featuring chess
D has a golfing connection
E is its own mirror image
F is (infinity/infinity)-1, you could argue
G is a European negative number
(Remember, no two letters give the same number!
Good luck!