"i would like to upgrade my graphic and processor,"
Processor is fine, only upgrade the graphics card. Don't worry too much about all those figures. Instead read a few independent reviews with benchmarks.
The HD5850 is considerably better than the HD5770, but so is the price!
If you go for the HD5770, then a Corsair 400W like click here with 1x PCI-E connector for £40 will be fine.
The HD5850 will require a PSU with 2x dedicated PCI-E connectors, & I'd get this Corsair 550W one click here.
Let us know your motherboard & PC case's brand+model. G
P.S. If you think you'll be running 2x of the above cards at any time in the future (dependent on your motherboard supporting CrossfireX), then get the Corsair 550W (link above) for 2xHD5770 & an Antec 750W click here for 2xHD5850