HI
I am in the British Gas plan and have had a similar problem in that My Vokera Eclipse sometimes switches itself off, no heating or hot water.  I have switched it off for a while, then back on again.  It re-sets itself.  The British gas Engineers, when they finally turn up, have not been able to find the problem (twice). Mine does lose a little water now and again, a friend seems to think that this may be the problem,  However I am at a loss.
                
 Milly
                
 March 2008