According to the ES Magazine this is the list of the finest day spas in London...
Spa NK
127-131 Westbourne Grove, W2
tel. 0207 727 8002
http://www.spacenk.co.uk/category/spa.do" onclick="window.open(this.href);return false;
The Cowshed
119 Portland Road, W11
tel. 0207 078 1944
http://www.cowshedonline.com" onclick="window.open(this.href);return false;
The May Fair Hotel Spa
Stratton Street W1
tel. 0207 915 2826
http://www.themayfairhotel.co.uk/spa" onclick="window.open(this.href);return false;
Ushvani
1 Cadogan Gardens SW3
tel. 0207 730 2888
http://www.ushvani.com" onclick="window.open(this.href);return false;
The Spa at Chancery Court
252 High Holborn
WC1
tel. 0207 829 7058
http://www.spachancerycourt.co.uk" onclick="window.open(this.href);return false;
The Intercontinental Spa
One Hamilton Place, Park Lane, W1
tel. 0207 318 8691
http://www.spaintercontinental.com" onclick="window.open(this.href);return false;
The Spa at Mandarin Oriental
66 Knightbridge, SW1
http://www.mandarinoriental.com" onclick="window.open(this.href);return false;
tel. 0207 838 9888
Elemis Day-Spa
2-3 Lancashire Court, W1
tel. 0870 410 4210
http://www.elemis.com" onclick="window.open(this.href);return false;