Right... Firstly thanks to Scotty for the instructions.
Here are some photo's
I used 2 dinner table knives to get the unit out, slide in both sides as per scotty's post then move the butt's of the knife's horizontally outwards so that the tips compress the clips inwards.
unplug the connectors
there are two screws that hold the back of the unit together, remove these and carefully fold back so not to desturb the ribbon cable. there are three Large bulbs behind the Display and one each behind the temperature controls and one in the middle for the button lights.
there is no need to dismantle the unit further, use a flat blade screwdriver to give the bulbs a quarter turn and they should remove.
If you disturb the ribbon cable ( or want to seperate the halfs) see photo... use your fingernails on eitherside of the clip to lift it up it should release the ribon cable, to re-instate, slide the ribbon in, home then push down the clip.
once i get a source for the bulbs i will post, or if someone knows...??? please post too.