There's a tendency, particularly in England to refer to an item by the name of the most popular brand of that item available.
Therefore, a vacuum cleaner becomes a Hoover, a cola becomes a Coke, a packet of condoms becomes a packet of Durex and so on and so forth. Sellotape, for example, is a brandname.
What's odd about this is that most people will accept any variation on the common theme, including a competing product to the one asked for. In other words, if you serve an English person a Pepsi when they've asked for a coke, no big deal.