Thought this seemed a good all round spec! Dell refurbished are usually pretty spotless, have 12 months warranty and there are also scratch and dent at £560 approx.
Inspiron 15 - 7566
Processor: Intel® Core™ i5-6300HQ Processor (4C,6M Cache, up to 3.20 GHz,45W)
Windows 10 Home (64bit)
8GB (1x8GB) 2400MHz SDRAM DDR4 Non-ECC
256 GB SATA III Solid State Hard Drive
No Optical Device
NVIDIA GeForce GTX 960 with 4GB
Intel Dual Band Wireless-AC 3165 802.11ac, 1x1, 2.4 & 5GHz + Bluetooth 4.0
LCD Back Cover - Black (Non-Touch Screen)
Battery : Primary 6-cell 74W/HR(Integrated)
15.6 inch FHD (1920 x 1080) Anti-Glare LED-Backlit Display
Internal English Non Backlit Keyboard
Can't really see anything wrong with the above for £560-610!
Recent, actual quad i5, 8gb RAM which is very likely to be upgradeable, decently sized SSD (which should also help with battery), full HD and reasonably usable dedicated graphics!