Help with low budget rig

If I did the exchange rate correctly, that would be about $365 USD. Trying to put together even a poor gaming rig at that price would be difficult. These choices are from Newegg in the US. I realize you won't be able to shop there if you are in Europe, but you can use it to find the items locally. Perhaps Ebuyer: http://www.ebuyer.com/store/Components
I'm not familiar enough with the retail places in Europe, so this is the best I can do. It comes to about $372 USD before shipping. It should game well up to about 1440x900 resolution.

Case: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Board: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Card: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
CPU: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
RAM: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
HDD: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Optical Drive: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

you know there's a UK version of pcpartpicker for convenience

It's hard to say exactly what a "decent rig for gaming" as it will vary from person to person. But, I can say I don't think anyone here will agree that you can do decent gaming at that budget. My advice, would be to wait up and save until you have AT LEAST $600 USD. Around $800 is where I would recommend though.

If saving is not an option, the above build seems to be your best bet.