Halfords Industrial rolling cabinet + top box for 399 here: http://www.halfords.com/workshop-tools/storage/tool-chests-cabinets?partnumber=169774,169790
I have the industrial range (same bundle as above), and it's brilliant tbh. I thought I'd fill it up immediately, as I had three large'ish tool boxes with stuff, but it's not even half full yet, so there's plenty of storage.
If you want to wait for a bit, I think they do the above deal around new years usually for 300 (that's what I paid in store last xmas). For 300 it's an absolutely stonking deal IMO, but even at 399 it's still very good for the money
Make sure you're collecting with an estate car, because the boxes are huge and wont fit in a saloon easily. I had to make two trips as I couldn't fit them into my 5 series.
Also, they're very heavy. I seem to recall the bottom cabinet weighs in at 75 kg... Massive pain to move around until you get the wheels on it.