I presume that you are in the UK? If not local wiring codes in your country will apply.
The wiring regulations in the UK are now BS 7671, 1992 (the old IEE Wiring Regulations).
The Regs are non specific on the point and say simply that surface mounted socket outlets on a wall should be at a height above the floor or adjacent work surface sufficient to minimise damage to the plug or cables. (Reg No:553-01- 06).
If I were you, I would install residual current earth trips, (RCD devices) and ensure that all workshop sockets are metal clad.
Mushroom panic buttons at strategic places are also a good idea in case you have to disconnect the juice pronto.
Hope this helps