Going by UK prices a Radeon 7850 is likely just out of your budget but worth the extra if you can afford it. Otherwise you may find a bargain on a Radeon 6950, 6870 or Nvidis 560Ti or 560 all of these are better than any newer generation cards as long as they are under 150 for the 6950/560Ti and under 125 for the 6870/560Ti thats based on a 7850 being 175 the tax where you are may change the value. If you can gewt any of the above then a Radeon 7770 is really the only choice.
With that graphics card I am amazed it plays at all....lol...
You NEED a better card..
All the best Brett
That's a bit of an unfair statement. Sure it's old but that cards decent.
I used to run Skyrim on High settings with a 9600 GSO.
More on topic, the rest of your Spec is fine for Skyrim, maybe a slightly better processor wouldn't go amiss and maybe a HD6/7 series card or nVidia GTX 5 series card. That'd easily achieve 60+ fps on max settings.