As has been said above, you’ve really got the conundrum of spend lots now, or spend less now and buy another replacement sooner.
The Toshiba you linked too doesn’t look that amazing spec for the money. True it’s got 8GB of RAM (which isn’t all that necessary), and a large HD, but only an i5 and doesn’t seem to have discrete graphics. Personally I’d be looking for an i7 and discrete graphics if possible, or at least an i5 with a very good discrete graphics card, with less RAM (this can be upgraded cheaper in the future) and a smaller HD (which I’d immediately replace for something faster than 5400rpm anyway).
Something like this… http://www.ebuyer.com/261157-acer-aspire-5750g-laptop-lx-rcf02-109
You’ll note the quad core i7 processor and discrete graphics, though less RAM and a smaller HD, but at just over 700 quid it’s a bit of a steal!
In fact, scratch that, just found this… http://www.ebuyer.com/279521-acer-aspire-5755g-laptop-lx-rpx02-037
Same machine, 10% faster processor, 2GB more ram and bigger HD for only £13 more!