Again something im as well is interested in.
Instinctively regarding RAM though i personally wouldnt want to run win on less than 1+ gig ram, preferrably 2 GB.

But i was thinking of getting a cloud vps (looked a bit at citycloud.se).
Only paying for what you use and being able to login to the adminpanel and allocate more resources at will means one can start small and allocate more memory etc if need arises just by changing your account settings.

Though dont know what backup / management demands you have, much hangs on that too.
Oh and regarding cpu cores. I dont know how knowledgabe you are regarding vps solutions, so i might

http://www.mycitycloud.com/ is their english site. Though i guess you perhaps want a british ip.

Yeah its all a matter of max pricetag versus performance in the end. I run my kooboo dev projects on a dual xeon e5520 / 12GB at the moment wich doesnt tell me much about performance. And havent had any vps servers earlier, except the ones i host myself. But i did try the citycloud free trial(the server is shut down automatically every 6 hours until one pay and before that only 512 meg / 1 core).
Did an testinstall of kooboo wich some site package and apart from the jit / caching at fist run(slower than my dev server but again, cant really compare), it functioned well, except the win rdp was a bit sluggish. Though that was on an empty clean installed installation so doesnt say very much.

I think generally its hard to compare '1 core, 1gig' between separete providers, urrent customer reviews is the thing i should go for. Since as ive understood that how resources are shared can widely differ. Then its up to what hypervisor they use, wich could in turn also make a difference.

And then again if the provider is flexible and can upgrade you if you need it then perhaps it can be profitable to go with the 4cores / 1gb and see how far you can go with it. But if you got the cash go for more is my tip. On can never have enough hardware! ;) Sidenot / fyi,4 core vps for that price i think they are shared cores, wich has advantages and disadvantages.

A sidenote: Eurovps has their datacenter in the netherlands correct? If you dont plan to host specifically british targeted sites i dont think it matters much. And im no SEO expert. But ive heard that host location can affect search engine rankings atleast to a limited extent. So if your webserver is seen to be hosted in holland and you for example has a british hotdog site with heavy search engine competition from other british hotdogs site it could affect atleast theoretically.
My tip therefor is to do some reading up on this as well, if you havent already taken this into account, before you dismiss it.