If you want to get away for a weekend is it possible just to turn up at say, Gatwick on a Friday night in the hope that there might be some last minute cheap flights to any destination that you can jump on for a weekend away - like a stand by thing? Or is this unrealistic these days?
I dont know how that would work. If you are a standby for a flight you have to be listed for it. You could go on the lastminute.com website and look at what is available. Gatwick on a Friday night, round the M25, for something or nothing - not a good idea!
Not as a standby. For that you would have to already have a standby ticket. This is usually if you work for an airline and have a free or reduced standby ticket. You can turn up at Gatwick and buy tickets for flights if available, but that would be full fare. I think you really would be best to find what you want before going to Gatwick.
Prior to the rise of budget airlines it was possible to simply turn up at an airport and negotiate with the staff on a ticket desk to see how low they'd go with a fare for a flight which was about to depart. A few 'full fare' airlines might still accept such practices (probably mainly on long haul flights) but all of the budget airlines will charge you the highest possible fare for immediate travel.