@David-TP success !!!!!!

I checked the QOS setting via the app, as suggested, and it was throttled to 1mb. I have disabled the QOS and now getting the expected speeds from the broadband.

I did not think that a firmware upgrade would have affected the QOS setting and I never thought of checking it

As the deco's are all now connected and working as expected, with the firmware and speed issues resolved. I am happy to close the fault down

Thanks for your help

Paul