Finished this on Saturday. Was relatively simple to do. Disappointed that the entire floor has been treated except the portion that is now visible. I am debating having someone spray the island or doing it myself. Worktop needs to change and hob needs to move to complete it, but happy with the size as the edge of the worktop is now in line with the edge of the cooker upright. when i replace the worktop, the overhang may be a little shorter. its currently 35cm to account for the hob to ensure that the space is usable in the meantime.

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.

Not due if you mean you want an island like this? 120 cm wide, 120cm length would be needed minimum just for the seating area side. That's assuming you would use a 60cm wide base unit in middle opening at side. Never saw anything like that to be honest. If you have island with seating on both sides you would need almost 2 m gap behind it if you were having units behind it so you could get by if someone was sitting at island

It is just a little bit tight for an island and so I would say no, making tight spaces just makes a kitchen feel small whereas leaving space makes it feel so much bigger.  I love DIY kitchens because they are so cost effective but I know the DIY side can be confusing so I have created a course of How to Design your Kitchen in a Weekend for pretty much anyone like you, planning to buy from places like DIY kitchens.  There is a free three day email course you can sign up to too which might be all the help you need! https://www.thekitchenladyuk.co.uk/lets-get-designing/Kitchen-Design-Course Might be worth a look!