This cache's is the 6th in the series, and the first multi in the series, another one which the kids should be able to get involved with. The shown location is not where the cache is found but the waypoints head in it's general direction, no more than 25 minutes stroll away.
Go to Waypoint 1 you are looking for some text on the Utilities Building (A)1 - 551(B).
Next go to Waypoint 2, dont catch a bus, just look for 7(C)2.
Then onto Waypoint 3, green box, white numbers 3(D).
And finally Waypoint 4, these numbers should light up F3 (E) NP
Simply work out the co-ordinates N 52 04.(E-B)8(C) W 000 43.(A)(D)(B).
Keep you eyes and emails open for the rest of the series over the Summer/Autumn 2015.
Cache is small with just room for a log and pencil but no reward for the FTF this time, sorry! :-(
Also sorry for the muck-up on the co-ords at go live FTF - DJ:CD - was a lucky chap who obviously knew his way round Green Park.