That's interesting keberoxu, because I've used 'deedy' all my life. It's often heard here in Norfolk, but also in West London in the fifties. It does, as you say, mean the same as 'handy' - useful, capable etc.

Our village shop is looked on as being 'handy' (It's closed at the moment for refurbishment, and we're all saying it'll be handy when it re-opens) In that context it means 'close at hand'.

We also say a gadget can be 'handy', for example I recently bought a tickling-stick duster from a door-to-door lad. It's very handy for getting behind radiators and the tops of curtain rails.
(The lad was a Nottingham Knocker though, and a bit of a crook!)