Yes they do, the maximum length is 100m, how do you think they could build networks in big office buildings otherwise?
Here is a link to a 10 m cable for 1.99
http://www.ebuyer.com/customer/produ...duct_uid=43770
And another to an Orange 30m cable, highlighting the trip hazard for £14.10
http://www.ebuyer.com/customer/produ...duct_uid=20788
Belkin ship direct from their own warehouse for ebuyer so the delivery is really reliable and quick.