If you didn't already know, it has 4 strings standardly tuned to 'G, C, E, A' and is a really easy instrument to start learning for anyone of all ages. It is about half the size of an acoustic guitar, and the base pitch is a lot higher. Like any instrument though, if you want to play something to a decent level you have to put in the hours of practice every week, stay dedicated and committed to achieve some minor or major success. Ukulele is no different.
You can purchase a beginner ukulele for less than £30 via any music retailer* and start learning straight away. I recommend either a soprano or concert ukulele to begin with. Soprano's are smaller than concert's but not by much.
Here's a basic chart showing the basic chords C, Am, F and G. You should be able to get these sounding clean within an hour or so.