What sort of music do you listen to? This will determine the basic criteria for amp and speakers.
If this is mainly for music, forget the idea of an a/v receiver and get a good integrated amp for around the 300 GBP mark. eBay is good. Don’t be afraid of 70’s and 80’s Japanese amps from JVC, Sony, Sansui etc. They can be serious bargains if you do your research. I’d avoid most boutique UK amps in that price range as they can prove problematic although there are some good ones from the like of quad and Cyrus that may just fall into your price range.
Speakers take the rest of your budget and here I would go UK boutique, mission, B&W, Tannoy etc. All made some cracking speakers but you really need to play some music through them before deciding.
If it was my money I’d be looking for a Technics class aa / vc-4 integrated amplifier and a pair of B&W floorstanding speakers. It won’t be the last word in detail but it will play music and not dissect it like some hiFi can.
There are a million correct answers to your question though but buy wisely and you should be able to flip though many combinations until you find the one you like best.
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