I use the C:geo Android App which is free and according to many, is better that the official (paid for) App.
There are loads of caches in Sussex, some great series to walk on the Downs and on the Ashdown Forest. One of my favourite has to be 'Crowborough Cluedo', a long walk starting & ending in Crowborough, taking you to Groombridge, skirting T. Wells and back through Eridge. Based on the Cluedo game you have to work out whodunnit, where and which weapon then calculate the coordinates for the hidden bonus cache.
Yes, it's Geeky (and I don't care!), but if you like walking and finding out more than you think you know about places, it's great fun.
PS. There's a cache hidden outside the Amex (part of the Star Wars series) so you could even pick up a find on a match day!
Does C: geo have the same caches and link to the official geocaching website? I may have to give it a try as have just switched from iphone to android and don't want to pay again!