Thanks for all comments. I like PWJ architects idea, but think our space would not do that door justice. I love the bi-fold acoustic fabric panel and will investigate that further. I do want to replace the door with something as an add on porch, no matter how well insulated, will always allow a cold or hot bank of air coming into the hall.

The door (and a fixed glass panel) are going in as a replacement for two windows and a pillar so the steel beam is already accounted for. I was more concerned about usability of sliding doors that tall.

sometimes its good to take a breath and really think about how you live - rather than all focus being on the plans, which can seem immovable. For example, I have a largely open plan ground floor but on the advice of my sister whose kids were older at the time, I kept a small snug living room that is separate and as my kids have grown up through teenage years that has been a saving grace - we can all go to separate places,! I dont have to listen to video games whilst cooking etc :) Does one person often watch tv and the other like to read? Where do hobbies take place? Would it be a simple solution to just turn that dining table round to make more space for those doors? If you like to entertain would you like to hide the mess inthe kitchen to be cleared up later? I for example insisted that I could close my kitchen off from the front room and hall (and stairwell) because one of my pet hates is cooking smells lingering everywhere! Also consider if the doors could be retro fitted - and l ive in the space for 9 months first to see if you really need/want them?

I had a 60's bungalow with these windows and needed to remove one when combining a bathroom and loo. In my opinion simply boarding over the frame would look a mess. To do the job properly I had to carefully remove the old brittle glass. Cut back the frame and create a rebate. Insert an additional stud, board over and skim with plaster. It's quite a fiddle but the materials are cheap if you have the tools and time. I employed a plasterer for skimming. I would strongly advise leaving things as they are, changing the glass if you prefer and spending your money elsewhere. If your other half can't live with the transom windows, and looking at your photos I would remove glass and frames, insert additional studs, board and skim. You could then extend the cornice right round the room but you might have to move the loft hatch over too. If you are considering altering your stairs your balustrade doesn't look like it would pass current building regulations. For child safety you must not be able to pass a tennis ball through any of the gaps. You don't have to change it but most professionals would want any upgrade to meet current regulations. Good luck with your new house.