Close to the cheapest price this lens has ever been available - the £160 Canon cash back gives a total price of £515, making this a bargain.
The 24-70 L 2.8 II is sharper, is a stop faster (but loses IS), but is over 3x the price at this deal..
Also available from Amazon, but they only have 2 in stock. https://www.amazon.co.uk/Canon-EF-24-70mm-USM-lens/dp/B00A2I1D56
Having previously purchased a lens that was backordered and subsequently arrived after the cash back promotion had finished, Canon did not honour the cash back - so be warned if this goes to backorder.