I do love a good slouchy bag and I really like this one from Delight. Large enough to stuff in all your... stuff, it's also got a nice floral lining. Oh and the strap is long enough to wear as an across-the-body bag.
It costs $258.50 and, don't forget, Delight ships to the UK.
Related: Zac Posen's red leather 'Ariel' shoulder bag | Red leather Beatnik bag | Saint Tropez hard-case clutch at Delight