>Hi Viv, that was it thank you - I thought PerSession meant the duration of the life of the app i.e. when I create the client it will stay alive until I close it but obviously not - thanks very much for your help you've obviously done a fair bit of WCF ?

Glad you got it sorted. Actually my WCF is a bit rusty (mostly just delivering JSON to browsers at the moment so WebApi is enough) - I had to look up a couple of things to fresh my memory :-}