I am looking for an electric oven (or maybe gas), that could be built in underneath a hob. My problem is that the space I have is only about 52cm wide, and I can’t find an oven that slim.
No such thing in the UK I`m afraid as you have already found they are all 60cm wide. The only thing you could do would be remove the hob, cut through the worktop and fit a 50cm freestanding gas or electric cooker. Only thing to remember is if you go for electric you will need to have a 45A supply back to the fuse board.