Welcome to the Community, I'm very sorry to learn about the problems you're experiencing with your On Demand service at the moment.
We are aware of some of the 319 error messages when trying to watch content from Sky and Channel 4 at the moment, is this what you're trying to watch?
Just in case that's not the case, I've located your account to run some tests on the set top box from our end for you. We're detecting some slight errors and if you've not got any access to the On Demand services, we'd like to send an engineer to come and take a closer look.
I've sent you information regarding this in a private message, which you can view by clicking the envelope on the top right of this page.