I'm no expert on Mesh systems but reviews say you need the higher spec ones if you have 100Mb/s internet and want it all available so the 5 series is going to be faster than the 3 series I have listed (and just bought). But if you just want streaming ability all over the house then the Currys...
£29.99 for a 3 unit lower spec one at Currys which is £40 at Amazon.
https://www.currys.co.uk/gbuk/computing-accessories/networking/whole-home-wi-fi-systems/tenda-nova-mw3-whole-home-wifi-system-triple-pack-10184407-pdt.html