Tassimo by Bosch cream & black coffee machine £33.99 at Amazon

I have a different tassimo machine, and find it awesome, there's a pretty good variety, and found the cheapest place to purchase them is directly from their website, there are always discount codes about, only annoying part is they increased the free delivery eligibility from £25 to £35, so just means you'll need to a bigger purchase in one go, but their delivery speeds are stellar, so if you run out of coffee, you could potentially get resupplied within 1-2 days!

I haven't looked into any other cheaper pod alternatives so not aware of any, I would recommend having a look at their website for the different pods:
tassimo.com/gb

When you purchase from their website, it also comes with their recycling pod program, which is also good for sustainability.