I wonder if maybe your planned snug is extremely small, compared to all the open plan space? Also, you seem unsure what it's going to be used for, which could lead to it becoming a 'nothing' room. It can't be both playroom and office without causing a lot of tension! Really think about how you like to use the different spaces in your house at the moment, and what is missing. I would personally use the intended snug as an office, use the current kitchen as a playroom - and keep those walls. I'd also build a new wall between the current dining room and kitchen to keep the office and playroom separate! Then I would remove the wall between the living room and conservatory and the dividing wall in the conservatory, put the dining room as you have on your plan, but move the kitchen to the bottom left corner of the drawing. That's just my opinion though - you have to think about what would work for you!

You need to put all the dimensions on for a real feel for the place. You would also need to instruct and architect and a structural engineer. A concept planner could really help to give you an idea of what's possible and open your eyes as to what changes could be made. I doubt you need to seat 22 on a daily basis, but you may be able to get two dining tables in on occasion. ( We keep another table and a set of chairs outside in a store room for such times ). We have one table that seats 8 all the time, then the other that we bring in which seats 6 more. It's a squeeze, but we manage. Thus I had a little shuffle about and came up with this as a 'concept idea'. Clearly specialists in their field will be able to help a lot more:-

We did love some of the suggestions above… but stuck with our original plan! Although we did change the kitchen layout from U-shaped to ”farmhouse” style, with the table in the middle and sink under the window overlooking the garden. The old dining room has become an office with two desks - partly due to COVID and the need to work from home and homeschool etc! We have also moved a lot of the children’s toy storage in here although they still bring things into the main lounge to play where there’s more room. At 8 and 5, they also actually now keep and play with a lot of toys in their rooms, so I think the old dining room will remain as more of a computer and homework room - it’s nice being able to shut the door! The ”study” on the plan is very much a workshop/gym/play room for my husband! We didnt want to sacrifice that space. It might turn into a teenage den later on perhaps, or even a downstairs bedroom for my Nan. The small upstairs bedroom has become a second office as I’m also still working from home (and my husband has too many meetings downstairs!). It houses our sofa bed too so acts as a spare room and my space to do yoga and sewing. Overall, we are pleased with how everything turned out. We quite like the option to have space away from each other and the flexibility to change the use of the different rooms. We do all spend a lot time together in either the kitchen or main lounge as plenty of space in both.

If you don't need the 4th bedroom downstairs, I'd move the office upstairs to the quietest room and then use the space downstairs for a bigger entrance hallway with storage space - also increase the utility space, probably combining utility with the hallway storage. Having a large utility/bootroom is really useful. Or you could add a downstairs toilet in the current office space too - provide it with the window to the front - but then you're not getting a wider hallway, just better storage off of it. Ideally, I'd rather make the ensuite shower room into a jack-and-jill type bathroom, with access from the guest bedroom as well as from the hall - removing that small cupboard behind the bedroom door and moving doors a little would work (and move toilet to be on the same wall as sink). Am not sure whether I'd rather the guest bedroom was the 'formal' lounge though, rather than having to walk all the way through the kitchen, the dining room and the other lounge area to get to it? Upstairs, if you really need a separate bathroom for each kid then I'd add one to the bottom right bedroom, with shower room in the bottom section of the top right bedroom. Middle bottom room gets the family bathroom to themselves, albeit not an ensuite, shared with the top right office.