Hi. More photos of the whole space would really help people to give proper suggestions, so give us some when you can. You have white, cream, grey, brown and black, from what you've told us and this pic. The grey could be the only jarring colour, but we need to see more. Well, at least I do before I suggest the backsplash tile colour and style and size! You can have stoves re-enamelled, but it could look great as is. Cleaning? Oven cleaner, elbow grease, washing up liquid, proper scourers - for the inside, that is. An extractor fan on a traditional stove with a sideways flue is going to be tough. Normally, you'd put this in a chimney breast or what looks like one. Anyway, post more pictures (and reassure us that you are going to move those sockets) and then I'm sure you'll get lots of great ideas coming your way.

Add a charcoal filter to the stainless steel hood to make it recirculating and add a small electric wall fan ( like expelair type ) where you marked the wall - as long as it extracts a min 60lps that should be ok for uk building Regs.

Normally i think islands in a small room work better if they’re in the same colour. Personally I prefer Matt and think shaker style would work. The kitchen will probably look bigger minus handles but I think shaker handleless are more expensive but might be wrong. You could have discreet handles anyway. Have you considered an induction hob? It’s sleeker and will give you more worktops space when not in use. It also looks as if you could have a deeper than normal worktop on the back run (more storage space)? i added some tiles for texture but you may hate the colour (Apologies for the bad photoshop!)

My extractor built into ceiling, ceiling is 2.6m, vents up and outside. It's above hob on island