A 17 inch decent gaming laptop for £700? This is hard...
For £750 you can get this Lenovo G780:
Range: G Series
Model Name: G780
Part Number: M842VUK (Dark Bronze)
Operating System: Windows 7 Home Premium 64 bit
Processor: Intel Core i7 3612QM 2.1 GHz
Memory: 8 Gb DDR3 1066 MHz
Memory Slot: 2 x SODIMM
Display: 17.3 inch LED Backlit HD display, 1366 x 768, 16:9 widescreen
Graphics: Nvidia GeForce GT 630M
Graphics Memory: 2 Gb
Sound: Integrated stereo speakers (2 x 1.5 W)
Integrated Camera: 0.3M integrated web camera
HDD: 1 Tb 5400 rpm SATA
Wired Ethernet LAN: 10/100
Wireless LAN: WiFi 802.11b/g/n
Bluetooth: BT v2.1
Interfaces: 2 x USB 3.0, 1 x USB 2.0, headphone/mic combo, VGA, HDMI, 2-in-1 card reader (SD, MMC)
Fingerprint Reader: ---
Security/Support: OneKey Recovery 7.0, McAfee Emerald 11.0, Veriface 4.0
Productivity: Energy Management 7.0, Adobe Reader 10.0 (backup and preinstall), Microsoft Office 2010 Starter
Power: AC Adapter 64 W
Battery: 6 Cell
Dimensions: 416 x 273 x 44.9 mm
Weight: 3.0 Kg
Warranty: 1 Year Collect and Return
Nice big pic here:
Don't be a fool and get a lesser spec just for the sake of paying £50 less. Go a little bit over your budget and get something decent. You probably won't find anything cheaper than this on those specs.
You could add a solid state disk as system drive later on, and the thing will fly.
Also try to learn about computers. Everyone can learn, ignorance is no excuse. Within 5 min. I managed to get all this info for you, Google is your friend. Teach yourself, pursue it even if it seems hard or scary at first. Most people look for easy fixes and always rely on others when things go tits up. A lot of those people are lazy fools, they'll never learn anything because they don't want to learn. They have the attention span of a caterpillar: As soon as they see a long post or a long technical article they can't be bothered to read it and give up straight away. Learn to rely on your own two hands. Put the time in, read, learn, all the info is out there at your disposal and FOR FREE. You can do it, and once you feel the confidence you'll never regret it.