"My budget is up to £1,000
I won't be using it for gaming
Will mostly be used for high speed internet, downloading and uploading, storing all my photos, music and videos. Live streaming. Hopefully running several different programmes at once without it crashing (!). That sort of idea": How long is a piece of string.
"I was thinking Sony": I have a Sony Vaio PC & a Sony Vaio Laptop, I have never been disapointed with either.
My advice is go for the best you can afford.
Nip in to PC World and let them show you what they have got for your price range.