Best laptop under £500 for intense multitasking

Im looking for the best laptop i can get for my needs under £460 British pounds and it has to be available in the UK for that price. I really liked the look of the Lenovo U series and the Dell 7000 series both of which i could afford in the US but not in the UK so you see the prices don't always correspond. I am hoping to study music at university and would use the laptop for my studies and for leisure. It would need to be able to cope with photo, video and sound editing, music notation software, word processing (so a good keyboard is a must), video streaming, and heavy other internet use all in combination with intense multitasking and remain FAST. It also should be able to last me a good few years without problems. I'm looking for an i5 processor a fair bit of RAM and storage (though im willing to compromise) and ideally a graphics card too though i understand they are hard to come by in my budget. The lighter it is the better but not a priority. I was going to get this:
http://www.ebuyer.com/584159-asus-x550cc-laptop-x550cc-...

Asus which seemed to meet all my needs and then i realised it had an ivy-bridge core rather than a haswell. What are your thoughts on this? Is a haswell that much better and should i really be looking for a 4th gen processor to the extent of compromising elsewhere or not?
If yes i found these:

http://www.ebay.co.uk/itm/Lenovo-G510-Intel-Core-i5-420...
(though that is ideally to heavy for me to carry round to lectures etc)

http://www.amazon.co.uk/Toshiba-Satellite-C55-A-1N1-15-...

http://www.staples.co.uk/satellite-c55-notebook-15-6-in...

and i really liked the Lenovo G50-70 but i couldnt find the i5 version within my budget but if you guys do...

Anyway, obviously if you guys think the ivy-bridge core asus is fine for me i will definately go with that; otherwise, what do you recommend?