You are kind of asking for too much.
The reason?
Software. Software maintenance and reliability is SUPER expensive. It costs tens of thousands, or hundreds of thousands of dollars a year to maintain the software on these devices to ensure they stay usable and functional. Pandora goes down? $50,000. Spotify stops working? $30,000. A security vulnerability is found? $250,000.
They can't sell their devices for next to nothing and still get usable functionality to an end user.
This is why products like Sonos and Bluesound cost a LOT more than your budget. It's because they aren't supported by advertising and additional sales the way Amazon devices are.
That means you really need to pair with a larger company, that isn't tied so much to additional sales, and that's a tough call. A cheaper product is something like the Yamaha MusicCast 20 at $250. I'm guessing pricing should be similar across the pond.
The Sonos One may be the cheapest option at about $200USD. Sonos has a history of solid performance, but this is still their cheapest speaker option and is still a bit over budget. It's absolutely about as cheap as I would go here.
Others may have some good ideas closer to your target budget, but even a better Echo product, like the Studio, is $200. So, you aren't getting good devices that listen to you all the time and try to sell you crap for under your budget right now.
I'm happy to hear if someone has some options for you though that may work within budget.
EDIT: Seems like the Ikea Symfonisk is a pretty good way to go:
SYMFONISK Sonos WiFi bookshelf speaker, white smart/gen 2 Place the speaker horizontally or vertically, or mount it on the wall to use as a practical shelf. Also helps you to use your space optimally, while providing a rich sound that fills the entire room. A collaboration between IKEA and Sonos!
www.ikea.com
