"Found 43,415 Flatshare, Rooms to Rent ads in London" Gumtree displays 55 ads per page. So, after looking through ~0.25% of the adverts, you concluded that the

"Found 43,415 Flatshare, Rooms to Rent ads in London" Gumtree displays 55 ads per page. So, after looking through ~0.25% of the adverts, you concluded that there was nothing cheaper than £300/month? Wow, that's pretty thorough! It took me less than five minutes to find a hostel-style roomshare for £7 per night (less than £220 per month).