In planning terms there is a 45 dec rule i.e draw a 45 dec horizontal line from the centre of the nearest first floor window of your neighbors house towards your house and your first floor extension should not pass this line

Do you require two doors into the kitchen/living space? If possible I would look at the options of removing the door on the right and moving the other door to left to line up with the front door in the hallway. It looks like you could pottentially gain a fair amoutn of space if this is possible.

Theres a bedroom and en suite above the garage so roof cant be raised. we’re going to get garage properly insulated and converted to a utility at back, storage at front. weve a decent size drive (3 cars fit) and corner plot with a good 4/5 metres to border at side, but as garden not that deep at back, and garden east facing with large side area south facing, its a good outdoor space to keep. i dont think we’re going to extend, its choice of keepinh as is (just doing garage into utility to move washing machine/tumbler/ironing board etc into there and free up space in kitchen), or knock through to make big lounge diner. with knock through though, still not sure what to do with galley bit in kitchen

If you're adding, not knocking down any of the existing structure, then the current kitchen is well positioned to have shower room and utility on the windowless wall and the connection between extension and dining room along the wall with the door. Existing plumbing isn't far from where you need it. Foundations will probably mean that you have to dog leg the windowless wall slightly for the extension but the silver lining is it giving you a tiny bit of outside wall to the utility for the extractor fans from shower room and utility (means shower extraction running through utility).