Much depends on how flexible you are about dates in addition to where you are flying from. By the way you frame the question you appear to assume there is only one place where you can possibly be living/based, and that in turn almost certainly means you are in greater London (where else...is there anywhere else ...?! :) ). There is a very useful tool available on www,.moneysavingexpert.com which allows you to skim the internet for cheap flights between your stipulated points over periods of time and at a price below your chosen maximum. Do make certain you are aware of the add-ons that airlines tend to include in the very final bill total. But the site only covers certain budget airlines, nevertheless it saves you a lot of work if you want to do a thorough search.