We have similar ones in, brand new, boxed, open to all networks. The offer of the 3310 was because of their liking for the "retro" stuff.
Have about half a dozen different ones, all brand new, under £30. Nokia, Samsung, Alcatel, and unlike some high street chains you don't have to buy any credit with them.
As a cheap/replacement/calls only mobile they're cheap. The Alcatel one takes two SIMs, useful for keeping your own/business number separate, a lot of people keep their private number in one slot and a throwaway SIM in the other for adverts (as above) so you don't get 100+ calls a day trying to get you to sign up for free boiler or reclaim your PPI.