This is the build I would recommend that fits into your budget. It has an i7 with hyper-threading and good GPU, although in the future I would add another 8GB KINGSTON HYPER-X BEAST DUAL-DDR3 2133MHz but for the time being 8gb should be fine
Processor (CPU)
Intel® Core™i7 Quad Core Processor i7-4790 (3.6GHz) 8MB Cache
Motherboard
Gigabyte Z97-HD3: ATX, LG1150, USB 3.0, SATA 6GBs
Memory (RAM)
8GB KINGSTON HYPER-X BEAST DUAL-DDR3 2133MHz X.M.P (1 x 8GB)
Graphics Card
2GB NVIDIA GEFORCE GTX 760 - 2 DVI, HDMI, DP - 3D Vision Ready
1st Hard Disk
250GB Samsung 840 EVO SSD, SATA 6Gb/s (upto 540MB/sR | 520MB/sW)
2nd Hard Disk
1TB WD CAVIAR BLACK WD1003FZEX, SATA 6 Gb/s, 64MB CACHE (7200rpm)
1st DVD/BLU-RAY Drive
24x DUAL LAYER DVD WRITER ±R/±RW/RAM
Power Supply
CORSAIR 550W VS SERIES™ VS-550 POWER SUPPLY
Processor Cooling
Corsair H55 Hydro Series High Performance CPU Cooler (£39)
Sound Card
Creative Sound Blaster® Audigy™ FX OEM (£28) (This depends on your audio needs)
Monitor
AOC I2769VM 27" IPS Monitor - 5ms, 1920x1080, D-Sub, HDMI, DP. (I personaly own this monitor and it is absolutely fantastic for video editing and the colour and quality is fantastic)