Your options are as follows
http://www.cameraworld.co.uk/canon-7...t-voucher.html
http://www.cameraworld.co.uk/sigma-7...5-6-dg-os.html
You can push the boat out and go for this
http://www.cameraworld.co.uk/sigma-1...-cashback.html
I toyed with it but the 150 min length put me off as I would be swapping lenses constantly plus reports say it does go a bit soft at the far end.