This is a helpful podcast if you are thinking about what size of kitchen island you want or what to go for: https://shows.acast.com/love-your-kitchen/episodes/exploring-function-over-aesthetics-with-amnda-hughes

Love your kitchen, you’ve done a great job, not only does the kitchen look good, it’s totally practical, drawers are the way forward, even if they are more expensive than cupboards. I’ve just redone a kitchen in a house we rent out, the old one was finally falling apart. I was going to go to Howdens and use the joiner etc we knew, but in the end we used a small local company, which cost us £300 more, but the quality of their interior cabinets and doors was so outstanding, plus they could do everything, including tiling, we went with them. We didn’t change the floor, but did everything necessary, I’m hoping it lasts well and our tenants look after it!

@kazzh Adding a wall as suggested by HU won't allow for the intention of an open plan with the living room as and adding a wall by the current opening will remove a lot of afternoon light from the living room. Adding the laundry to the pantry is certainly possible, it's an idea that has been considered, but we didn't know a) how possible it was to create a new waste pipe and where to run to, possibly the bathroom next door. b) how to position the pantry area to consider a reduced length of waste pipe to avoid a mass of disruption of other units ie cutting holes in them. Moving the patio door isn't impossible, as we can just brick up the current and add a window, then add a patio door to the extension. Thank you so much so far!

One option could be to make the sitting room bigger, than you have drawn, to fit a large sofa and creat a corridor behind the stairs with cloaks cupboard, then the kitchen on the left with island peninsular facing the garden and the extensions forming the dining/seating areas