Has the Revo PiXiS RX been updated yet. Yes.
What other MPEG-DASH BBC On Demand radios are out there for less than £150? BTW don't care about DAB or FM.
Less than £150? Not a lot.... Roberts Stream 93i you can probably find for under £150 (and it's a pretty good radio), but other DASHing radios (Roberts Revival iStream2, Roberts R-Line radios, Revo SuperSystem and SuperConnect) are more expensive. Some recent models from other brands may also be capable - it requires firmware level V2.10 or better.
I can recommend this https://www.amazon.co.uk/Zettaly-Portable-Bluetooth-Speaker-Internet/dp/B00WR3W2TA/ref=sr_1_1?s=electronics&ie=UTF8&qid=1479835789&sr=1-1&keywords=zetally+avy
I've had one for quite a while now and it's been excellent. It's basically an Android tablet within a radio case. It runs BBC iPlayer Radio which gives full "on demand" coverage rather than the Podcasts only that you get from the Revo Pixis RX. I have both and I prefer the Zetally for sound quality and flexibility. It can run anything an Android tablet can run, so Youtube, Tunein Radio, Spotify are all available. It's battery powered so genuinely portable, though I have mine permanently connected to mains power. It also has a remote control but I can't say how useful this is since I haven't used it.