Added the wrong photo of my suggestions…

Here’s the current floorplan (we have knocked the wall down between the kitchen and dining room and swapped them round, but the floor space is the same)

This one!

And what do you hope to gain from extending? (other than a larger kitchen dining area)

I know the question is about the rear, but may i ask what you intend to use the new reception room for? (Because i see a kitchen-diner and a utility, but no extra bathroom and such.)

We are extending to get a kitchen/dining/ living space. We have 3 small children (under 4 years old) so having a good living/ play space in the kitchen is important. The utility is also important longer term (I hate having piles of muddy shoes by the back door!). Room at the front will be a study/ have a sofa bed for guests.
Thanks!

i would advice to put the study/guest bedroom in the middle, as it far from driveway noise, I placed the utility in front because it faster to reach, if you come home drenched, you get in take off coat and straight to shower

I agree that there isn’t enough room for an island with stools and a dining table. Moving the utility makes no difference to the width of this space. I think you should either build bigger or abandon the island

Extending about 2m at the full rear (and 4m on the side):

I left two columns in, because i'm no structural engineer. Moved the toilet to create a hallway towards mudroom/utility. The basin in the study is merely as a reminder to get plumbing prepped there, just in case. As water in a playroom would be irresistable, right? But there's plenty space next to the dining table for toys, as they will likely still want to be near you.

Another with that 4m sideways, but without the rear extension:

When you accept the lounge area as being the one and only, there'd still be lots of extra's added to the house with extending sideways. Here's a study/guest/play with it's own ensuite. Toilet moved over to create a hallway to a utility (3.9x2.5 in this floorplan) where all those little boots and coats could be stored! Oh and i closed off the front reception doorway and added ensuite doors.

Thanks everyone, appreciate the suggestions! Most important is to have the separate living space in the kitchen and I’m not sure we can achieve that. We could potentially go another 1.5m to the side and extend to the boundary. The garden is sloped otherwise we would just do a standard 4m extension along the back.

Keep the side path, very practical. And when it comes to the rear, a retaining wall could be an option? How far out can you go without having to dig deeper than +/- 1 meter? (photo perhaps?)

Another metre to the side would make a huge difference.

Thanks everyone.

Jonathan, your latest plan would be ideal.

Ideally we would leave an access gap down the side of the house, does anyone know how big this should be (at a minimum)?

RInked, I will take a photo of the garden tomorrow. If we extend at the back we will need to push the retaining wall back, but for the current extension size, it’s not a huge job (my husband could help as he did the current wall there). Pics incoming when its light again!

90cm but preferably 120cm, for example mini excavators come in 70-100cm widths