I am aware that Halfords have had the buy one get one half price offer on the 591's but in case you miss that or you only need the one I've found a car garage that sells them for £55 plus delivery. That's at least £20 cheaper than anywhere else.
They come in a plain box rather than Thule branded and are a Nissan dealer extra by the looks of it but who cars, it's the same 591 in the box with the same fixings. mine just arrived today 🙂
http://www.sandicliffeshop.co.uk/search,i.html?category=732&q=thule+591
Bought some 591's from Sandicliffe earlier this year via ebay for the same price, they were the cheapest I could find.
They only charge one lot of delivery irrespective of how many you order (I ordered three and only paid 1x £5 delivery).
100% the same Thule branded carrier/fittings as the one I already had, as you say just in a plain box.
That is a good deal. FIL just got a pair from Halfords, two for. £119 including delivery or reserve/ collect which I thought was a good deal.