£340 for a Core i5 6GB Toshiba laptop? I'd have their hands off... I'd think that was seriously good value. The cheapest I can find that model on eBay is £466 - +£70 postage from the US. (If it makes any difference, I'd suggest the model you're looking at is a US model). I wouldn't have too many doubts about its graphics capability: the integrated graphics that come with the Core i5 are supposed to be pretty good - and editing video is a memory hog, but the 6GB should be more than sufficient. Online performance should be just fine. I'd say: go for it.
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