Where to start to improve appearance of house?

[CorgiOfDoom]

Apologies for lengthy post.

I moved in with DP four years ago. It's his former marital home bought around 25 years ago, exW moved out in 2005. Up to that point,having seen photos, it seems the house was attractive and well cared for.

But he's hardly done anything to the house since she left. And now it's a scruffy mess that looks outdated. He runs two businesses and works long hours, has little interest in the house as long as it's clean.
I WFH so spend all day here and it's now doing my head in!
Every room needs attention and even from the outside it's clearly sad and unloved.
l know it could be a great house, but I don't know how to make it feel fresh and welcoming with a limited budget.

We have planning permission for a small ground floor extension which will give us a modern kitchen diner, but we can't start work on it until next Spring at the earliest.

I'm concerned that when the renovations start there is going to be a lot of mess to the ground floor so am rather wary about e.g replacing flooring or decorating just now.

Any suggestions or advice would be great.

TLDR: house neglected for 15 years +, it's a mess, suggestions and advice please on how to give it some TLC to make it feel like a home.

Wait until the extension is done. You will be glad you did trust me!
At the most I would do a fresh coat of paint, deep clean, get some cheap throws for the sofas and buy some big plants.
But anything you do now will get trashed by the builders even if you think they have no reason to go in that room...

I've renovated 2 houses btw.

Yes wait until the extension is built, (Ive renovated 3 houses). If there is wall paper on the walls and paint to strip or sand you could start doing that over winter in rooms you don't use much. Also go through everything and have a good clear out. If you can sell in on eBay or facebook and money can go towards new things.
Think about what bathroom and kitchen you want, where to buy it, the lead in times. Then you can get it all done fairly quickly next spring

I'd buy paint, vinyl flooring and makeover all the rooms I could now. I'd also sell or giveaway any furniture I didn't love or couldn't makeover with paint and wallpaper and get new stuff from Facebook marketplace and freebie sites.

I'd even tile paint and cupboard paint the kitchen for now.

I also agree with waiting until after the extension when doing it so soon; however, as this is doing your head in -- get the concerns out of your head, go through the whole place from front to back and make a list and then group that list together however makes sense for you. Have it somewhere you trust to go back to later and add thoughts as they come to you to get it out of your head. You can prioritize it better later when it's all down (and even more after a declutter as a pp said).

There may be a few maintenance tasks that you can do now that will make a difference for you like dealing with squeaky gates or trimming back plants or dealing with broken things. I got possibly too happy replacing the dead doorbell with one that rings and pings my phone so I can stop wondering if I've heard the door or not.

Do the basic infrastructure work - does it need rewiring, what’s the heating system like, does it have enough hot water for a really good shower, are the windows and doors sound... then think about the way the house flows - are you going to make any other changes to rooms? I would then think about the bathroom... I agree with others that I would leave decorative/aesthetic works until the extension is done - the mess and dust is honestly unimaginable - and better to save money for lovely things once that is completed.

Do you own the house now?

Well you can do upstairs and the front outside, just leave down stairs and the back. Surely that’s enough to be cracking on with?

Are you going to be investing your own money in it? Do you have any claim to the house or is it just your partners. Start with the unaffected bits of garden and outside while waiting for extension

I'd also leave anything major til after works are done, but decluttering/re-arranging furniture & getting some cheap throws and pillows could make a difference in the meantime

Great advice, thank you all.
We're off to the garden centre tomorrow to make a start on the outside.

WRT financials, we have a cohabitation agreement written up when I moved in (80%-20% for house) but are getting married in October.