I don't recall ever seeing a river specific pole, there's not really a market for it in the UK. Many of the poles with carp somewhere in the name (they stick carp on almost anything, it sells) or description will be fine. Just ignore the stuff designed for elastics well in excess of 20, and you'll have an all-rounder. A £500 pole is going to come with more than one top-kit. You don't have to put the maximum rated elastics in them all.
With half an eye on your location, I'd also suggest that you give serious thought to the river venues you are intending on using the pole. Poles are fine on the slower, deeper and more turbid sections of lower rivers. On faster, shallower and clearer upper reaches, they can be all but useless. Putting a pole over a fishes head in clear water can be the kiss of death. In the dim and distant past, I have used a pole on the Lower Tees, Nene and Middle/Tidal Trent. I wouldn't even bother on my more local clear, shallow rivers.