Hello and thanks for your prompt reply. The drawings provided show that the support beams are 203mm depth and therefore they will be too big to sit inside the ceiling void. As the weight per linear m is 23Kg as detailed on the drawings it may be worth asking the engineer to reduce the depth and and increase the weight so the beam can be inserted into the ceiling void. I note that there is also a couple of posts in the stud wall and these could be upgraded if necessary. I do not make these suggestions lightly. The main benefit of inserting the beam inside the ceiling is the removal of the shadow cast on the ceiling. The return nibs on either end could be cut back and if needed posts could be fixed direct to the brickwork to provide vertical support. There may need to be a spreader plate welded to the bottom of the post in order to mitigate the point load on the foundation. Obviously this is more of a structural design issue. Is there a good reason for not centring the bifold doors to the external wall? You have so much height on the flat roof why not put a warm deck roof on instead of a cold deck with in cross ventilation? Can I also suggest a warm pitched roof too. You may find Web Dynamics TLX Goldto be a very useful form of insulation as you will only need about 75mm of PIR insulation in between the rafters. I've never been fortunate enough to meet a building control officer willing to accept a heavy duty Catnic lintel over a 4M bifold door. I thought the under stairs might be the position of the meters. I would consider relocating these to an outside wall. Then turn the WC through 90 degrees and design it under the stairs. If I was planning a kitchen diner extension with a beautiful bi-fold door looking out into the rear garden would try and create a direct flow from front of house to the back. I would move the utility room into the middle of the house to provide a direct line of sight from the front door to the rear garden. GD3 would provide access into the utility room. I'd consider moving the door along the living room wall so it could open into the hallway. This would allow a 950mm wide fully glazed door to be placed between the hallway and the kitchen diner. With regard to the position of the new extension wall which is adjacent to your adjoining neighbour I suggest that you look up the party wall act 1996 booklet online here - https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/523010/Party_Wall_etc__Act_1996_-_Explanatory_Booklet.pdf The part that is of interest is "Line of junction - building astride the boundary". If you build across the boundary you should gain at least 150mm of additional internal floor space along the length of the outside wall. Also if in the future your neighbour decides to build an extension they can utilise your wall for if they pay half of the cost of its construction. I'm sure you know that you are responsible for paying all of the costs from all sides relating to the party wall agreement. If the neighbour on the other side is within 3/6m then you will need an agreement with them as well. The architects drawing indicates that the drain is not adopted or shared and therefore you will not require a build over agreement with the water authority. Best wishes Andrew

Thank you both for your suggestions and apologies for the delay in replying. @CWD It's my fault but I didn't mention that the bottom window is south facing and over our garden so not sure we could make that work unfortunately but thank you so much for taking the time to help. Your point about how much we hang vs fold could be a really useful point to consider with space saving, thanks! Could you explain what you meant about that and having the bed backing onto the walk-in dressing space please? @katlucy also thank you so much, again totally my fault for not mentioning but our heating system has all the pipework coming down from the loft in that cupboard outside the guest bedroom which I don't think we could easily or affordably change unfortunately. So still stratching my head how to make it work but, honestly, thank you so much for those ideas as I've been struggling to come up with anything new so hopefully seeing these might spark something! If anyone happens to have any other ideas, hugely grateful for any and all comments! Thank you 💛

Move bathroom upstairs with small extension to exend kitchen into a dining space keeping shower room as a utility. using the front of existing kitchen for a sofa area

Reduce the living area size to prioritise the kitchen and dining.