I would not class a system with 2 GB of RAM to be one to ignore, however the fact it has Vista on is something I would suggest avoiding. My experience with Windows 7 is that 2 GB of RAM is perfectly usable. I had some issues with networking, and that's why I gave a brand new Compaq (reduced 250 quid when Asda Living wanted to make space in February 2010) to my BiL, who then installed all his engineering and business applications on it. Have had no complaints or shrieks for help from Staffordshire so assume all is OK!
However, depending on your budget, you might find the local shops (especially with people willing to "find the extra" to provide a present for Christmas) have Windows 7 systems at 200 pounds and more (based on my regular checks at the local CEX, CashGenerator and CashConverter).
I tend to look for Windows XP (which is pretty stable and I have a load of suitable software ready to install) but fewer and fewer XP systems are to be found on the shelves.
There are some deals to be had on Ebay - I got a Dell Inspiron for about 85 quid in the summer - but well worth checking the ones with a 'Buy It Now' price and contacting them (15 minutes before their listing closes) to make an offer. If no-one has bought it at the price they wanted, they may relist it, perhaps with a 'make an offer' option.
Also worth checking whether it is a business listing it - the seller may be paranoid about getting anything less than 5 stars for everything, so the description should be completely correct.
Finally, look for Tesco Outlet, Argos and Ebuyer Express selling off systems (it means their primary online sites can have the newest models and the older cheaper ones are not found there for comparison against costly newer ones). (Why bother with Tesco, Argos or Ebuyer ? You should get 12 month warranty with anything they sell.)