Each council will have its own policy on what their bin men (er, sorry, 'refuse disposal operatives') are allowed to take. However the safest thing is to take it to your local household waste recycling centre.
Alternatively you can take it to any store that sells electrical items, since EU regulations require that all such stores must provide recycling facilities.
e.g. you can take it into PC World (irrespective of whether you bought it from there or whether you're buying your new printer from there):
https://www.pcworld.co.uk/gbuk/recycle-874-theme.html
While you're there, buy one of these printers (because they're by far the best value on offer at the moment):
https://www.pcworld.co.uk/gbuk/computing-accessories/printers-scanners-and-ink/printers/canon-pixma-mg5750-all-in-one-wireless-inkjet-printer-10143745-pdt.html
Ignore the headline price of £99.99 because you get £50 off with the discount code, so it's actually £49.99. It's a superb printer and, because it uses separate cartridges for the coloured inks, it will work out far cheaper to run than the £30 printers that put all of the colours into a single cartridge.