I think you can use the space with or without the walls. Even if you can't do the utility wall i would personally lose the kitchen wall. Would make the kitchen feel much bigger x

I would take down the kitchen wall but keep utility ,sometimes things can be too open,having a utility keeps things hidden washing etc and opening up the kitchen wall will make a great space

Thanks both. I've now realised my plan isn't clear...we would build another wall to enclose the smaller utility. Have attached an updated plan which I hope is accurate!

Anyway I can edit a post?

So, to clarify, we would remove the kitchen wall & also the utility wall & build a new wall keeping the utility enclosed. We would then form a new entrance into the playroom as we would only be losing walk-in space in there. By doing this we would gain an extra 2.1m for the kitchen/diner.

Would you consider having a utility cabinet to gain even more space ? ie put washing machine and tumble dryer in a cabinet with ironing board and basket storage. I know I dump the newly washed /dried laundry on the dining table to sort it - so this could give you easier access to do the same ?

We'd prefer an enclosed utility, probably adding a new door from from the dining area so that we no longer have to enter via the conservatory (whoever added the extension to this house didn't think it through properly!). On the plan the red outlines are the open plan kitchen/diner that would be created by knocking down the kitchen wall & moving the utility wall. We'd make a new entrance to the playroom so that no useable space in that room would be wasted. We did think about encorporating all of the utility into the open plan & slicing off the top of the playroom too but then we'd lose the area in the playroom where we have a sofa that is used by the kids a lot.

Why not take both walls down to pony height x

Now thinking knocking down the utility wall won't work as that's the only place we can put the dining room table & there just wouldn't be enough space. The plan was to turn the table 90 degrees & move it closer to the new utility wall but then it would be a tight squeeze to access the playroom from the new playroom door. Headache!!!!