Low cost but function laptop?

I have been considering getting a laptop however I don’t want to spend a huge amount of money on it.

Of course there are Laptops like the eeePC and the OLPC however these are rather low spec.

As this would be my only laptop it needs to be reasonably functional. At least 25-30 Gig hard drive. Enough processor to run things like Eclipse and compile programs reasonably. WiFi is a must and obviously it must be capable of running Linux (though not necessarily pre-installed). As cheap as possible would be nice, preferably under £300 (though maybe a bit more depending on the features). I do not need to run Windows on the machine, I have Windows on my dual boot PC and rarely run it any more so paying extra to get something Windows compatible would be a waste.

I am considering eeePC and using either SD cards or an external hard drive but carrying round an external drive could be tiresome and would drain the battery much faster.

Another option is using second hand refurbished laptops. Which companies sell these and waht is the best way of going about getting one? Do people think they are worth it it would it be better to buy a brand new machine (Considering I am on a budget).

Anyone here have any suggestions or advice, particularly with respect to checking whether laptops will work well with Linux?