If it is definitely more of a snug I'd go for a long sofa opposite the fire, probably a chaise as it may be be more comfy for tv viewing. A window seat would look good and lovely for reading etc. If you're doing bookcases, consider matching but with a shelf left out for the tv. If there's room i might then add a couple of small accent chairs angled in front of the bookcase. If you were to use it formally (I know you said not) but would go for 2 sofas opposite each other at right angles to the fire with the tv opposite the fire. As Tavolla said, do measure carefully! It's good to draw everything to scale or cut out paper templates

Although it closes off the lounge, it makes for a better kitchen, so i'd probably go for something like this. Besides which, not everyone wants their main lounge open to a kitchen / diner.

Many thanks for the comments and suggestions. Regarding the toilet, we really don't need one as we have one separate in the room next door. It is also more convenient with the kids as one can be in the bathroom while the other uses the toilet. Having had more play with the designer tool, I came up with 2 others options. Note, that we only have 85cm each side of the window so if the shower is towards the external wall, it is limited to 800. v3 - in this one, the shower is 800x1000. Could potentially have built-in storage at the foot of the bath. My main concern is that the shower is quite small and it creates a corridor effect between the door and the shower. v4 - in this one, shower is still narrower but must longer at 800x1200 and bathtub is 1700. I also was able to put some cabinets for storage/towels - but not sure if it is very accessible (does it need to be?) It feels a bit busy and I would have love to give the kids a bigger shower (as they are growing) but not possible with the window location. We are thinking that version 4 is probably the best option at the moment. any suggestions? Many thanks

Hi Jessli, we have a blog post all about mistakes to avoid when you extend your home which you may find useful. I have linked this below, if you would like to take a read😊 https://www.thelivinghouse.co.uk/blog-interior-design-tips/the-6-most-common-mistakes-we-see-when-you-extend-your-home You may also find our Facebook group community helpful, its another place to ask questions and gain free advice from like minded interior lovers and us as experts! Here is the link if you would like to join - https://www.facebook.com/groups/interiorhomedesignadviceandsupportuk