You'd be hard pressed to find a cheaper Android based smartphone than the Samsung Galaxy Apollo; at £29.90 (from Carphone Warehouse's subsidiary Mobiles.co.uk) with a £10 compulsory top up (from T-Mobile or from Vodafone), it is even cheaper than many feature phones on the market and like almost all Carphone Warehouse smartphones is likely to be unlocked.
Note that the phone is refurbished and will not come with the branded box and accessories but it is still a very decent handset. Launched in July 2010, it has a 400 by 240 pixels 3.2-inch capacitive touchscreen display, a rarity at this price, a Samsung S5P6422 processor clocked at 667 MHz (the equivalent of the ubiquitous Qualcomm MSM7227), 256MB RAM, 512MB ROM, WiFi, Bluetooth 3.0, microUSB, a three megapixel camera and Android 2.1 Eclair (upgradable to Froyo) with TouchWiz 3.0 and Samsung Hub.
Similar priced phones at Mobiles.co.uk include the Nokia 201 black, the Alcatel OT 380 and the OT710, the LG Cookie and the LG Viewty Snap, all of which are feature phones rather smartphones.
Source : Mobiles.co.uk