Where in London can I take a Canon EOS350D SLR camera to have the inner lenses professionally cleaned?

Its a bit dirty inside & previous attempts to correct it have only made it worse..

There used to be a very good camera shop on the corner of Sidmouth Street near tavistock place!

Directly opposite Charing Cross main train station is a
camera shop.From the tube Trafalgar Sq or Leicester
Sq.There is a Jessops or was at Tottenham Court Rd.