I do find it odd that a modern cordless telephone works from the Sky hub but an older 'phone doesn't - assuming the cordless 'phone is a standard one rather than designed specifically to run from the hub.
What presumably won't work with the hub is loop-disconnect (pulse) dialling - though there are work-arounds for this (such as a
Rotatone fitted in the 'phone or a
Dialgizmo interposed between the 'phone and the hub) if the problem of older 'phones not working with the hub can be solved.