Saw the recent Boots deal relating to these which had sadly ended. Searched and found these on the Argos website, which are cheaper and promoted as less than half price.
Also available in pink: http://www.argos.co.uk/product/2582409
and plain for cheaper again: http://www.argos.co.uk/product/3768703
Free delivery and click and collect if available locally!
Official description as follows...
We've designed the unique, easy-latch-on teat shape with breastfeeding experts to mimic the natural flex, stretch and movement of a mums breast. Together with the bottles super-sensitive valve, this encourages your babys intuitive feeding action for comfortable, relaxed feeding.