Four week stay in Central London

Can any Londoners recommend somewhere to stay, for around four weeks late March/April in Central London? Something like an aparthotel or even an apartment on a month's lease?
Prefer close to West End but not Mayfair or Knightsbridge prices! Must have self-catering facilities and internet connection. Don't really know where to start looking so any tips much appreciated!!

[honey lamb]

Last year some friends and I stayed here at Scala House and found it very good. It was just off the Tottenham Court Road and round the corner from Goodge Street tube station. There were plenty of resturants and supermarkets nearby