Tried this in PC world and (The missus and Daughter having walked away in embarrassment) got £30 knocked off a laptop. Was very pleased with myself until a month later they were flogging the same ones for about £70 less. Was happy in my ignorance until the missus insisted on showing me the new price , I maintained it was a different machine entirely of course. Bottom line is you don't really know what anyone selling will budge by unless you try. Pay what your happy to pay and don't look back or move on.Haggling in independent shops is more common than you may think in the UK, and you'd probably be surprised to see how often it happens.
The supermarket chains make haggling almost impossible but it's worth trying if you're buying a TV or other electrical item with a damaged box or on display.