In reply to Phil79:
You could buy a pay-as-you-go smart-phone and as such not worry about a monthly contract of £20-25 per month. This does have its benefits provided you don't want to do a lot of internet surfing with a 3G contract. You can still surf on your phone with a WiFi signal though for free provided you have permission such as at home or a free HotSpot.
You can get some excellent smart-phones cheap if you bought them outright. For example, last year my Samsung Ace was priced just under £200 to buy but now you can buy them for around £60. As it is my phone is on a 2 year contract and in 12 months, it will be mine and by then I will have payed Virgin Media £312 for the privilage a contract.
I have to admit that my phone does not have the whistles and bells of a Samsung S3 but I can make it do anything I want, including using the GPS feature to pin-point where I am on a digital OS map. And I still get access to the same apps as all the other Android phones on Google.play site.
The GPS signal is very accurate on my Samsung Ace, the battery life is shite though, especially when using GPS. This isn't a problem if you are running/cycling around for a few hours and even if you are out for longer it only takes a few seconds to pop in a fresh battery which cost a couple of quid to buy.
I never knew how useful a smart-phone was until I played with mine for a year. During that time I discovered new and exciting ways to use it beyond my initial purpose of GPS mapping while walking on the hills.