I've designed loads of steep gardens. They need careful consideration to work well. Measure the level change carefully (or get it professionally surveyed). They start planning it out on paper to make sure you can fit everything in. The danger is that you start by the house and create your largest seating/entertaining area here, then get to the top of the garden and end up with a steep bank that is not useful for anything. The general rule is that more small walls are better than one large, looming retaining wall. Invest in the garden structure (retaining walls) then make use of the levels. Create different rooms at different levels to give the garden some interest and ensure that you can use all the garden. Create an interesting journey around the garden and put a seating area in the sunniest spot. Soften walls by running steps parallel to the house rather than straight up the garden. Make use of the level changes with water features and cascading planting.

If you're still keen on a flexible-function room (i.e. where the middle internal space works as a guest bedroom or family space for example playroom, snug TV room, office, hobby room), my suggestion would be to use pocket internal doors; and/or glazed internal french doors. Then most of the time the doors can be open and part of the open-plan. Then when using the the space as a guest bedroom, the doors could have roller blinds or curtains, to separate the space and add privacy. Consider which way you want the "flexi room" to open up. Rather than open up to the side of the house (near proposed cloakroom); I think it would be nicer if the room opens into the back room or the front room (likely to be much nicer views and better light).

Hi, I agree with the comments above. I absolutely love bi folding doors and would definitely consider these to be able to create fantastic indoor , outdoor living for summer living. From experience with kids and day to day living... I would have a large extending dining table that leads directly out onto the garden and move your family space to where your dining room is and have a tv etc positioned there with a more formal, grown up living room area as you have it in the plan. The key changes I would make are then to the design of the utility room which I would keep with access to the garage. Great for coming into the house with grubby boots and shopping etc . I would make this a reasonable size and I would also incorporate a cloakroom on the ground floor for family and guests to use without needing to go upstairs. I think this model would work well for a family and will give all the family different zoned areas to relax, do homework, have great dinner parties or casual eating. I would also add a table and chairs and if you have room in the garden, a casual seating area, bbq etc, parasol and take advantage of the whole open plan contemporary living of your new extension. Very exciting.. good luck.

Definitely no way!! You would regret losing part of the view to the garden. And it just doesn't make sense to have a bathroom off kitchen. Either do as bagpuss' plan above, or use that whole space for a shower/ bathroom if you need more facilities. If it was me, I'd like a utility area somewhere, perhaps you could combine this with shower room? Or have two separate rooms, wc and a single wall utility. If you do any laundry at home it is useful to have a dedicated space for this. Mine is approx 1.5m square but I'd be lost without it!! Attached pic of one Houzz one I like (seems to have popped into the middle somehow!) Wouldn't have to be this big even. And although it depends on your budget, I'd definitely try and get a pitch roof or a lantern in that ceiling to let in more natural light.