The Kindles are still sold with and without special offers on Amazon.co.uk? The only one where there is no mention of ads is the Voyage (and I presume it is sold without any ads as standard). Even the Fire tablets are sold with and without ads, although you don't see those options until the add to basket and configure button is clicked.
Basic Kindle - £59.99 is the default price 'With Special Offers', or £69.99 'Without Special Offers'
http://www.amazon.co.uk/dp/B00KDRUCJY/
Just be aware that there is a possibility the one you have spotted may well be with ads and you'll have no way of knowing until you buy it, and then may have to pay £10 to have them removed by Amazon. Also, there is a risk to buying second hand, if the Kindle has been lost or stolen, it could be blacklisted, and then when you go to register it, you won't be able to do so.