I have no problem with the idea of slowing down data after a certain point of usage as long as:
1 - The point at which you get slowed down is clearly advertised and the network (and ISP in terms of landline use) give easy options to see how much data you have used so far that month.
2 - The speed you get slowed down to is still actually usable for modern day smartphone usage (maybe not enough for streaming netflix or large file downloads but certainly it should be enough for music streaming, app downloads and youtube etc).
3 - There is the option to buy more "fast" data at a reasonable cost (ie not half the price of what I pay a month anyway!).

Otherwise it just seems like a con tbh.

Each to their own I suppose, but using Spotify on a phone must be one of the most efficient ways invented of throwing money away. Surely you can load a big selection of songs as mp3s, which you can listen to as often as you like without them costing you anything (depending on where they come from).

I've got 9,550 songs stored locally on my iPhone, but I still use spotify. I like to seek out new music and new artists and spotify is a great way of doing that.

How is it throwing money away? It's free. To stream it when I'm out I connect to my internet on my phone, again costing nothing as its unlimited.

And you can download Spotify tracks for offline playing too if you prefer.

I didn't realise you were on an unlimited tariff. It makes my 200 megabytes a month on a 1 gigabyte allowance look a bit low.

Ahh i see