There are only three visible screws on the back of this telephone and
it hasn't clicked easily apart after removing them: are there other
screws under the rubber feet or are there some other tricks I ought to
know about?

The problem I'm trying to fix is that suddenly, none of the buttons
operate any more. I can pick up and chat on an incoming call but can't
read menus, dial numbers or anything else.

My guess is that an internal connector had become an internal
disconnector but if the groups experience suggests something different
or that it's totally stuffed, I'd be grateful to know. I have another
working-when-I-last-used-it handset but thanks to Sod's Law it's in a
cupboard being held closed by two strings full of Christmas cards and
decorations. I'd prefer not to take them down just yet if the original
phone is easily fixable.

Thanks - and happy remainder of Chriastmas Day to all!

Nick