Maybe look at a netbook with the new N550 processor. Its Dual Core and the netbook i am using can cope brilliantly with multiple tabs and programs running in the background without strain or lack of performance
I bought this netbook with the same frame of mind, something small and portable, and can be used for web browsing, emails, word and some skype here and there. i am currently writing a review on it, maybe you can have a brief look at it, its nothing flash as its my first review so it might be a little simple and not as much in depth as other reviews can be.
As for the low end laptops, there are many out there for £300 or just over. The Acer TravelMate 8371 is a good little laptop, at 13.3" its ideal for what you want it for. there is a thread in this section, you might want to look at that.
If you want something portable but below £300 mark youcan find the HP Mini 311 out and about which has an Atom N270 processor but with an nVidia LE Ion Chip which is a step up on graphics compared to many other small netbooks. The Mini 311 is an 11.6" netbook with the same resolution as the Acer 8371 but with the Acer, you can get dedicated ATI graphics, i think its the ATI Mobility HD4330 or something close to that, which will be better than the ION of the HP Mini 311. But then again, the processor inside the Acer TM 8371 is a 1.4GHz Dual Core i think so it might be the better choice.
There are many netbooks and small laptops out in the market, its a case of finding deals and looking at reviews, which you probably already know

just keep an eye out and try and get hands on with netbooks and small laptops at local computer retailers, something which you have again probably already looked into.
Goodluck and Happy New Year!