The parking is not ideal and you would be better to arrive at Finchley Road Tube (Jubilee and Metropolitan Lines). Canfield Gardens is on your right as you come out of the tube.
The following buses stop at Finchley Road Tube Station: 13, 82, 113; However, 187 and 268 stop just outside the O2 Centre in Finchley Road.
West Hampstead British Rail is also not far away and links onto the Jubilee line if walking is not your thing!