Shopto.net have now started their official christmas sale, and i noticed that the Play TV add-on is in there at only £44 which is the cheapest i've seen it so far.
Play TV + PlayStation 3 TV Tuner
PlayTV lets you record TV while playing games, and offers live television broadcasts to handheld PSP consoles via the Internet.
With PlayTV, you can watch, pause and record free-to-air digital television while you take a break from gaming, further expanding the entertainment possibilities of the PlayStation 3. The PlayTV Tuner, which plugs into one of the PS3 system's USB ports, is capable of showing and recording both standard and High Definition channels where available, and will allow you to record one channel while watching another. It features a programme guide which lets you view listings and schedule recordings for the following week.
If you have a PSP, you can take all these features with you. As long as you are within range of a Wireless Internet connection, Remote Play enables you to watch live television, access previously recorded programmes and organise your media library.