You'll need to check the cost of the connecting to the sewage pipes from the bathroom above your new WC, they can be surprisingly high.

Do you need garden access from the new kitchen/living room space, you mention a window but not garden/yard access?

I'd also think about the circulation space, the very rough picture below allows you access around the ground floor and minimises the congestion at your front door. I've drawn a pocket door from the living room to that space so it can be open or closed.

..?

Thanks for the response Su L, fortunately my brother does plumbing/electrics so costs will be just for running the additional pipework and materials for the new WC 😁. I’ve also thought about maybe adding an ensuite to the main bedroom as it’s just the other side of the bathroom. But again don’t want to get carried with costs. I have considered putting double doors in instead of the window at the rear of the new kitchen (old utility room) but yes there is already rear access on the side of that part of the house (just before the shower room) so it would mean bricking that up. I’m thinking installing an L shape kitchen, with low level units running across the rear with the sink centralised under the new large window and the other units coming down the left side. I see what you mean about the circulation. The door can’t go into the snug (current dining room) from there as the head room is too low but maybe it can on that adjoining wall. Great idea thank you!

Would this work for you? I'd rather have the relaxing area away from the front door. You might fit both utility and a small shower room in the old kitchen. If the current extension could take the weight, I'd put the new ensuite on top of it.

Wow Tab Darcy thank you for this! Plenty of food for thought here! I definitely hadn’t thought about extending the upstairs for a new master suite but I do love that idea. I’d put the ensuite in a different position in that room tho as the house has a relatively small rear garden but it backs onto open fields so that bedroom would have great views, but thank you I will look into this! I have a structural engineer coming on Saturday so may ask a few questions about it and the potential costs involved. Also your kitchen/dining/living room is an interesting layout. It’s not shown on the floor plan but there is a chimney breast on the left side in the current lounge area so I just immediately thought that’ll be the tv/sofa end. Kitchen on one wall with an island I will now also ponder! I will attach a photo of the current lounge so you can see how big the chimney breast is at that end of the room.

Ah that does make it quite narrow, considering that it is the only way of getting to the back of the house. Your engineer could look at moving ghe stairs so there's a corridor?

Yeah it is quite narrow. Where would you relocate the stairs too? Sounds expensive 😬😬. Atleast one of those walls that I’m removing between the current lounge and utility room will be load bearing.. trying to limit costs if possible

With the left being narrow, could the attached work? It means losing a snug but better flow. The door from hall to living room would reman in place for emergencies but not be used daily. Right hand room could have a large, airy utility / hobby room, using internal glazing to bring light into the new hallway.

If you want to add master bedroom on 2nd floor extension I would advise this layout so you can get small WIC

How did the meeting with the structural engineer go?

Been told today I need to leave 500mm at either end of the load bearing wall. That will avoid the need for the extra work of side steels and digging foundations. So not a bad result. The overall look shouldn’t be compromised.