I nearly bought this lens the other month from the same retailer on the same offer. It's a really nice lens, although I've read it's slow to focus. In the end I decided to wait until I get a 5DmkIII for more benefit on FF and went for a 60D instead.
By the way, if that lens isn't currently in stock, good luck getting any form of response from Jessops. They are literally the worst company I've ever dealt with. Whoever posts on Twitter from them told me they'd point out my problems to the customer service manager, and I still haven't heard anything. They are deliberately vague in their ETA for the camera "soon", "shortly" and the latest reply I got after badgering them was "mid June, but we can't guarantee that", followed by "we are in contact with Canon, daily". If this is the case, an update to someone that just shelled out over £1000 with them would be nice.
To say I'm annoyed is an understatement, and I'll never use them again. A month ago today I ordered the camera (which was showing as in stock when I ordered it), and I've had 2 emails from them, and only after I phoned and complained that they weren't replying.