I would recommend/go back to City Nails. The one thing I didn't like was the threading chair was in the salon where everyone was getting their pedis/nails done so I felt a bit exposed. Very quick though and did a lovely job with my nails. A tad expensive but I guess it is Central London.
Good pedicure and the massage was awesome. Lady who did my pedicure was lovely. But another lady who took payment was super abrupt and lacks in customer service.