How to find a decently-priced studio flat in London?
Well, London (especially West London) is very expensive: you might have to relax your criteria a bit. Houseshares and flatshares are a lot cheaper than one-room flats: it’s worth looking at those. I’ve lived in quite a few and normal people tend to massively outnumber the nutters. Especially in the more expensive houseshares (which you’ll be looking at) it tends to be young, single-ish working people; not students who party loudly all night or dodgy illegals. I think places like Acton, Willesden and Harlesden are likely to be a bit cheaper: you might want to expand your area a little. Try looking at the Tube and train stations where you work/study, then follow the lines out until you find an area you can afford.
Bear in mind that the word “studio” is the kiss of death for flat-hunting. It signals (rightly or wrongly) to agents that you’re the sort of person willing to pay over the odds to secure a particular lifestyle; and you’ll find that even reputable agents have a definition of “studio” that is probably a bit more loose than your own (encompassing such things as “bedsit” and “this flat has fewer internal walls than one seems structurally sound”). And as you’ve found, its one of the key words that unscrupulous agencies love to use in their teaser listings for phantom properties – the too-good-to-be-true deals that get you to call up, so they can offer you worse properties at higher prices. And yes, look to the West and the North of Shepherd’s Bush for the more affordable places.