Hi all,
Many thanks for your input. I finally got to the bottom of the problem. On speaking with a (very patient) Sky technician last night (a prompt response to my written query to Sky), we went through, firstly all the options for the fault, (which I had already ticked off, one by one).
He then suggested turning off Sky Broadband Shield. I replied that I had already done that. The technician told me that he could it was still working?? So we switched it off, and the Apps started working again!
I then looked more closely at the Sky Broadband Shield web page, which gives options for age viewing. I realised that the reason that I thought it was switched off is that the switched off option is shown as a circle with a cross in the middle, which I mistook as that being my option- which it wasn't , if I'd taken more time, and looked more closely!
Everything working fine- but still leaves the question -why did the Apps stop running in the first place. The technician suggested it's because they are all run and owned by Mark Zuckerberg's Meta organisation- they must have altered their safety settings?
Thanks for the suggestions!