my neptune exotic shower?

my neptune exotic shower 9.5kw is either running red hot or freezing cold. so it seems to not have any control of temp could any one suggest what the problem could be cheers
j e, August 2012
Lack of flow causes this, eaither a blocked spray head, or simply turn it to a lower setting, if that fails call National shower spares on 0845 126 4141 or visit www.shower-spares.co.uk

Gary, September 2012