How do I bathroom / kitchen / extension? etc.

I wanted to do this but ended up moving instead; dining room at front of the house, kitchen in the middle (range cooker in the chimney breast) and then living room overlooking the south facing garden. I found a few precedents online at the time (classic trawl of the modern house, mostly) but all lost to the wind now.

A friend of mine in a swanky place out west (admittedly with a bit more room to play with) went one further with the kitchen at the front, dining in the middle and living at the back. His place is great, but I don't know whether that's the concept or just the effect of having spent so much money fitting it out with shiny things.

dining room is a bit of a hallway

This is a common problem that I have spent far too long thinking about. Looks like your place is the same as mine (i.e. 15 foot wide terrace). Basically there are two options to avoid the hallway / awkward middle room problem:

1. Kitchen in the middle: efficient on space, nice room at the back but you lose the opportunity to have a massive food prep space with island etc
   
2. Central "utility / WC core" with open plan kitchen-diner at the back and slightly enlarged front room. Lose the ability to close off the kitchen but can go more fancy with it. Get a slightly nicer living room at the front (rather than a snug) but most likely it will be dark.
   

https://www.themodernhouse.com/past-sales/stockwell-park-crescent/
http://b-vds.co.uk/projects/tonal-terrace/
https://www.osullivanskoufoglou.com/riversdaleroad
https://www.osullivanskoufoglou.com/grovepark
https://www.themodernhouse.com/wp-content/uploads/Highbury-New-Park.pdf
https://www.themodernhouse.com/past-sales/herbert-street/
https://www.themodernhouse.com/past-sales/howden-street/

few variations here