The best Android phone right now is the HTC One. No contest really. Build quality on par if not better than that of an iPhone 5, screen is fantastic (and full HD if that matters to you), really very very fast and the only Android phone I have owned that can tempt me away from my iPhone 5 for long enough to swap sims for a few hours.
The three drawbacks are as follows:
1. Sense UI 5, better than Sense UI 4 but it is an acquired taste.
2. You depend on HTC to get their phones updated with the latest Android version (applies to all non Nexus phones but HTC are notoriously slow on updating their phones)
3. Battery life is fairly poor, though to be expected given the spec of the phone.
If you just want to play with Android to see if you can get on with it get a Nexus 4. At 279£ it is a comparative bargain with great spec and a nice screen and build quality though not anyway near as good as the HTC One. It is also unlocked at that price so you can put your current sim in it without hassle. If you decide Android is not for you you will have no problem selling it as they are quite in demand given the price.
You might also want to keep an eye for what is coming in iOS7 as it is rumoured to be a fairly major rewrite. Personally I have owned a Nexus, a Nexus 4 and an HTC One but I keep returning to iOS as my main daily platform.