The ZTE Axon 7 and the OnePlus 3 are two very decent chinese phones, I bet you could get them for about 300 pound.They beat phones that are twice as expensive in certain aspects. I'd go for the OnePlus 3(personal opinion).
The Vodafone Smart Ultra 6 and the Vodafone Moto G are both excellent budget phones.
That being said a new thing I have noticed are the Chinese phones you can buy from Aliexpress.com. For a similar price you can get a top spec phone. For example the UMI Super 4G LTE 5.5 Inch Helio P10 MT6755 Octa Core Smartphone 4GB RAM 32GB ROM 4000mAh 1920*1080 5.0MP+13.0MP Android 6.0 is selling for about £150 and has everything you can think of.
My friend recently bought one and I was very impressed with it when he showed me it. Just wish I had known about it before I bought the Vodafone Smart Ultra 6 lol.
I wouldnt personally buy a z3 or z5 compact.
They're truly great featured phones but the z3 suffers constant screen & glass back breakages from out of nowhere & the z5 suffers overheating.
On a premium performance level the one plus one is still hard to beat at £199 retail , the one plus 2 is good but not worth the £50 premium.
Out of the fairly budget Chinese brands , the ulefone power , oppo find ,& especially the huawei p8 are very very good phones.
The p8 is on a par with the oneplus
The ulefone & oppo are mtk octacore chipsets & while great for general use the msli GPU on them struggles with 3d gaming at 1080p.
The ulefone is incredible value for £130 though & has a 6amp battery that can last for 3-4 days (it also charges from flat in around 2 hours)
The ZTE Axon 7 and the OnePlus 3 are two very decent chinese phones, I bet you could get them for about 300 pound.They beat phones that are twice as expensive in certain aspects. I'd go for the OnePlus 3(personal opinion).