Finding People for Jobs in UK

I have a whole load of well paid Web Applications development jobs in Hammersmith, London UK but in spite of advertisng them at the top end of the salary curve can’t find anyone. We are talking Senior .net developer/team leader, Senior and Middle Project Mangers, Applications Support and an HCI design specialist(not technology, the actual information retieval management Human Computer Interface.
Is there somewhere here I can trawl for people? Maybe someone can look at my ads and tell me what I’m doing wrong?