Need to find few banks in London to open an account for non UK resident.
It must have online banking.

There is a list of banks that are members of the British Bankers Association at:
http://www.bba.org.uk/bba/jsp/polopoly.jsp?d=103&a=1562

For foreign banks operating in this country, please see the Foreign
Banks and Securities Houses Association's web site at
http://www.fbsa.org.uk/

They have two leaflets in pdf form that may be useful. They outline
the identity and security processes involved in opening a UK bank
account.
International students - Opening a UK bank account
Opening a bank account if you are new or returning to the UK

Both are downloadable from
http://www.bba.org.uk/bba/jsp/polopoly.jsp?d=138

Many UK banks have separate offshore banking operations if you wish to
be outside the UK tax and regulatory regimes. Some are listed at:
http://www.uknetguide.co.uk/Finance/Banks_and_Banking/Offshore_Banking.html
http://www.financelink.co.uk/offshore_banking/

Owain