I need a bag! What would you choose?

[FluffySocksAndMarshmallows]

Criteria:

It needs to be as cheap as possible :(
It needs to be big enough to hold an A4 notebook, a diary, lunch, my purse, etc.
It needs to be light, if possible.
I don't mind colours/styles too much, but I will need to wear it with a few different outfits - work dresses, suits, etc.

I've checked Accessorize and the ASOS clearance but I'm terrible at making decisions.

Help me, wise ones!

How much is cheap as possible?
Dune shopper, £24
Plain shopper £7.50 (guessing not what you're looking for though
Oilcloth - looks a good size £22

Black shopper £20

Same brand and price different shape?

Ebay have some fabulous bags. My current bag was £6.

£20
£25