This seems a pretty good deal for a decent phone. The K550i seems to generally go for over £100 (even Orange's reconditioned ones are £55) and this one has a free Sony Ericsson Bluetooth headset and £10 Tesco airtime. I'm assuming that as this isn't a normal deal, the headset will be boxed separately and therefore can easily become a gift for someone (i.e. 2 gifts for the price of one!). The K550i seems to be the old K750i in budget clothing with some newer features whilst still retaining the Cyber Shot auto focus bits.
Check out the link below for a comprehensive review:http://www.mobile-review.com/review/sonyericsson-k550-en.shtml
Seems you can pick this one up in stores too but you can't check until you sign in/up.
Re checking this it's not too clear whether the headset is included. It is however inferred by the description (which points it out as opposed to the others which don't) and it's the only phone pictured with one specifically. See what you guys think, or even know!