You can get a HP Touchpad on e-bay or google shopping for less than £170, the OS as standard is WebOS which is a fantastic OS and the integration with the your phone, if it's also WebOS is great (i.e: you can call/text from the TP once it's paired to the phone), unfortunately with all the messing about between Palm being useless, HP buying Palm, HP Killing WebOS devices and HP open sourcing WebOS there hasn't been much love from developers and the amount of apps is severely lacking.
However, it is possible to install Android on a TouchPad, in fact, considering you can dual boot between WebOS and Android I think this will be my project for this afternoon!