Temporary housing

Moving into London and planning to get temporary housing until we find a flat. If it'll take about a month, maybe longer or shorter, can you guys recommend any cheap places to stay that'll be flexible on the length? I'd rather not reserve something temporary for a month and a half only to move into a flat in a month and waste the other half month.

I was originally thinking something off AirBNB.com or a cheaper hostel. Are there better alternatives? We're thinking of looking for a flat somewhere near the Archway station (my job in on the Northern Line), so staying in that area temporarily would be cool too, though not required, if that helps at all.

Thanks for any help.

If you are willing to airbnb, you could also try a temporary flat share, subletting someone else's room while they are on holiday or whatever. I would look at Gumtree.com for this. Usually pretty cheap and cheerful.