Currently Being ModeratedJan 31, 2013 5:17 AM (in response to K_squared)
Your system can support up to 8GB of memory and may require an EFI update. See this memory page on OWCs site. OWC is a recommended vendor for memory, along with Crucial.
Currently Being ModeratedJan 31, 2013 7:31 AM (in response to BGreg)
Thanks very much BGreg, much appreciated. I'm based in the UK - do you know any reputable retailers? No problem if not, I'll have a proper look this weekend, if not.