Memory manufacturer Kingston has a good reputation in the memory market and it has two lines of modules, ValueRAM and HyperX. The first line of memory is as the name suggests a value option that is meant for system upgrades. The HyperX modules are targeting high-end users and overclockers.
Oddly enough it appears that 2GB of 1,333MHz DDR3 ValueRAM will cost you a whopping £87 more than 2GB of 1,375MHz DDR3 HyperX memory.
Online e-tailer CCL Computers is listing the 2GB of DDR3 ValueRAM for £390.22 inc. VAT while the 2GBs of HyperX is listed at £303.55 inc VAT.
This doesn't quite make sense, but if you're out shopping for DDR3 memory, you might as well get the faster HyperX modules, especially as they're listed to have 7-7-7 timings compared to 8-8-8 for the ValueRAM.
You can find the ValueRAM modules here and the HyperX modules here