Delayed post, but my thoughts:
I've bought at least 4, maybe 5 cases from OcUK, but they've all been low end. That's the only region where the prices were competitive. Most of them were Akasa and Coolermaster.
I went to another popular online UK store for my P182SE, purely as OcUK did not have stock of it at the time.
I recently bought an Antec Micro Fusion for £69.99 including delivery from another online UK store. The OcUK price is nowhere near this (whether it was a special offer or not, the price was still much less), and I can see that a lot of the high end cases with low turnover are fairly highly priced, which isn't unreasonable I suppose. The price discrepancy isn't usually much, and OcUK have always been very good to me, but with that case it was huge so I'd be stupid to get it here. That said, I don't mind paying a little extra for OcUK quality of service.
Overall the range of cases is very good, and there's little cheap tacky nasty stuff that a lot of other places sell. However, the prices can be sometimes uncompetitive and it'd be nice to see some good special offers on them, especially as case prices seem to have rocketed since the downturn.