Do You know any good laptops for work AND gaming (just casual games like the sims 4, minecraft don't starve etc.) for under £1000?

Go on ebay some good deals now

Attention: Desktop > laptops, every day of the week especially for gaming.

btw of those examples the system requirements are hugely different, sims 4 requires quite a beefy set up, minecraft will run with most peoples specs.

Try omen from HP, there's some cheap models that can run recent games. Mine is a old model with a gtx960m and I can play games like vampyr with high settings. And yeah also sims 4 and minecraft with some fancy shaders. I paid 600 USD for it, I bet you can get a better one with £1000.

You have a fairly poor definition of "casual" games as The Sims 4 has some moderate graphical demands & Minecraft can be demanding if you utilize some mods. HOWEVER, there are such laptops available within your price range. Please note that I'll be running in US Dollars… So the £1,000 (UK) comes out to ~$1,337.10 US (based on current exchange rate at time of writing).

One to consider would be the HP Pavilion Power Laptop 15 series. Their current base model starts at $930 (~£695.52 UK, excluding any discounts, shipping & applicable taxes) which includes a Nvidia GTX 1050 graphics card, Intel Core i7-8750H processor, 8 GB RAM, 1 TB 5400 RPM HDD + 16 GB Optane Memory. Which would be good for what you want to do & more. For more savings, there's the previous year's models to consider.

* HP Onyx Blizzard Ci7 -- ~$800 (~£598.30 UK) -- Intel Core i7-7700HQ, Nvidia GTX 1050, 12 GB RAM, 1 TB 7200 RPM HHD
* HP Onyx Blizzard Ci5 -- ~$720 (~£538.48 UK) -- Intel Core i5-7300HQ, AMD RX550, 12 GB RAM, 1 TB 7200 RPM HHD

These aren't high-end gaming PC's, but specs are respectable enough to handle games under default settings without all the flashiness (like RGB lighting nor the bulk). One bit of "gaming flash" that is included is a backlit keyboard (using neutral white LED's) that can be turned off. This is a fairly nice feature to have when using the laptop at night or in poorly lit areas (as you can see all the keys).

With Dell, the Inspiron 15 7000 Gaming series with similar specs to the HP Onyx Blizzard Ci7 (only 4 GB less RAM by comparison) would run around $1,050 (~£785.57 UK) BEFORE discounts, shipping & taxes.

In due course of full disclosure, I do own the HP Onyx Blizzard Ci7 laptop that I got on clearance at work (for $675 US / ~£504.99 UK, before taxes) as they were making space for the newer gaming-geared systems. I just hope this gives you some ideas on what to look at before making your purchase.