Every family has their own amount of storage requirements - some small some huge - so very much depends on where you fit in beteeen ! Without the extension - if you put the dining in the playroom it would work ? If you only need the dining table occasionally - maybe have a clever table - either pulled up into ceiling when not required then clipped to floor to keep it from moving when in use - or a fold down table - or smaller extendable table etc etc but remember you will need storage for the toys - and a store cupboard for gold up chairs too ! ( this could - in theory - be the same cupboard !)

They should absolutely have put acro props in. These are steel props which look flimsy but carry a surprising amount of weight. My mum's just doing this with her flat. The buildings inspector came round and specified how many props and where they had to go before anything was touched. The RSJs were specified by a structural engineer and also passed by the building inspector. It's a vital part of getting it passed by building regs without which you'll have serious problems when you come to sell, even if it is safe. If there are acro props up, get in touch with building regs before it goes any further.If there are no acro props up, phone another builder and ask them if they can put some props up ASAP. A good builder should automatically prioritise it over any other jobs they have since it's a super quick and also urgent job but will probably want it in writing that someone else took the wall down. Also get in touch with building control (building control is the department which issues building regs and will send a building inspector). The exception to all this is if the wall is not structural but that's unlikely if there's a floor above it and impossible if there's another wall directly above. Also, your builder must by law have public liability insurance for if this sort of thing goes wrong. I can't give any sort of time frame for this. It's likely that any damage is already done but possible that cracks are propagating over time and may cause more damage if you leave it. It's entirely possible everything will be fine even without props. I've seen some awful things including a case where a man with obvious mental health problems took out all the walls in the basement of a 3-story building without using props and it somehow still didn't fall down.

For some reason photos in a different order, but so one from door in the middle! Thanks in advance for your help.

These photos look good. It would be lovely if the tv-hearth would be on the opposite wall (and the radiator moved), so the sofa could go sideways (and not be in front of the hallway door..), but that would be quite a project. Perhaps a custom built media cabinet opposite the sofa, plus an extra chair where the tv is in the photo?