Thank you so much for all your advice, everyone. I'd willingly pay an electrician to install the new cooker but I had one installer arrive who said he could not install the cooker because the box was "illegal" and he was "not able to fit a new box". My main dilemma is this is rural North Wales and NO ONE will do the job! One electrician said he was fully booked until end of September 2018 and none of the others will even return phone calls! I cannot find an electrician to come to the Betws-y-Coed area. We would do it ourselves and are pretty handy with 'normal' DIY, woodwork, simple plumbing etc, but is installing the new cooker something we can safely do ourselves? Or can anyone find an electrician in this area?? Many thanks again!