R1 and the Dark Rock Pro 3 have about the same thermal performance. The D15 outperforms both of them by about 5C but costs £10 more and is over £80. Basically the spread between these coolers in terms of thermals is 2-5C. So it would be better to go by price and looks since none of them are dramatically better than the others in terms of cooling performance. You can eliminate the DH15 because it's generally slightly over £80 although it would offer the best performance even if it's only a few degrees. The D14 is halfway between D15 and R1 in terms of performance an noise.
I'd go with the Dark Rock Pro 3 personally. It performs almost as good as a Noctua D15 and is only 1-2dB louder. It's
considerably quieter than an R1 while performing the same. It also has an advantage over Noctua (IMO) that it uses black fans instead of the less sightly brown/beige Noctua ones. Dark Rock Pro 3 is about as beefy as it gets and it's dead quiet as well.
https://www.amazon.co.uk/Be-Quiet-BK019-Dark-Heatsink/dp/B00HPX7J4K/ref=sr_1_1?s=computers&ie=UTF8&qid=1521237983&sr=1-1&keywords=dark+rock+pro+3