As new, laptops at that price are the ole- good enough for student stuff, sorta thing, Word/exel - forget any illusions of gaming above rts.
Dell bang some out for £299, in this sorta class.
Acer laptops are very good, imo of course (cos I got 2 - zero problems in 2 years lol), however thier ones worth their meat `new` are £500++.
In the 2nd hand variety, u could probably pick up the ones I bought for £600+ a few years ago, floating around ebay in great numbers I`d imagine.
What kind of performance do u need for this `mixing` ??