Hi Yasin,
You'd be better with a remap rather than a chip. The remap can be made to be tailored to your car whereas the chip can't.
The remap will give you more power and torque and potentially better mpg but it all depends whether youll get the initial outlay back in fuel. This will depend on how long you intend to keep the car for.
Also you'll have to notify your insurance company that it's been remapped which may increase your insurance. They may ask you for another £50-£100 which is cost you'll have to factor into the remap/fuel cost dilema. If you don't tell your insurers it's been remapped, then you'll void your insurance.
Cheers
Steve