You've had some great advice already and I'm going to add and reiterate some points. I'm not a developer but I have moved house far more than the average person and will always sort out my house a bit prior to selling so that it goes quick.
Front garden pic is too much hard standing, proportionally the house is about a quarter of the pic when it should be the main feature. Big pots fully of flowers and zoom in on the house a bit.
Downstairs layout. Do not make this more open plan, just make better use of what you have. That middle room with no windows. Dress it as a cinema room/ library/home office. paint it dark, fill it with books, soft lighting and comfy sofas. Embrace that it has no windows.
The lounge is great, put the bureau that is currently in the middle room in the lounge where you have that long rug, make it look like that's why you've moved the sofa forward. Pull the curtains back properly and let all the lovely light in.
Don't touch the utility, though if you have the funds I'd add a downstairs loo here.
Give yourself a hallway at the front of the house. You can do this with furniture. Take out cabinets to ensure you can do this if needed. Floor to ceiling wardrobe on the right as you face the front door inside the house. Leave a doorway width at the end so you can get into the long thin room. I can't quite tell if you have the width to do the same the other side and keep a decent size hall, so if not build a simple stud wall. Add hooks
The kitchen feels very dated. I'd paint the cabinets, probably white or sage green. I'd board and then lino over the tiles with something much more neutral and plain. Ultimately this is the thing most likely to be putting people off the house. Make it look bright and fresh. Will your dining table fit in the kitchen?
The long thin room. Remove the cabinets, make good the walls. Remove the fish tank. Consider adding a door to the lounge. Dress this as a lounge diner. Give yourself a gorgeous little breakfast nook at the window end with an L shaped bench and large round table. Big vase of flowers there. Big sofa and telly down the other end.
Add load of plants everywhere, all rooms.
Upstairs, reduce the amount of random bits of furniture and make sure all bedrooms have beds. use large blankets to make beds look neater without having to iron bedding everyone there's a viewing. Paint the brown wardrobes white.
You could recarpet if you've got the funds.
I think the bathrooms are ok and wouldn't do anything with these. If you can improve the rest of the house people will compromise on the odd thing they might want to redo. Most people want move in ready, not a project.
It's easier to sell a house if there is one wow room, especially if its a kitchen, but really you just want the house to tell a story about how safe, warm and lovely it is to live in. Not every room has to be special but they all have to feel clean and welcoming and have a clear purpose. You can't rely on people to have imagination, tell a story with furniture and 'stuff' to show people how they could live in a house.
I'd love a house like this. Best of luck.