Here is a good matched pair with low latency (CAS2), it's not ideal for overclocking as it's only pc3200 (XMS3200) RAM, anything higher is good for overclocking but is also more expensive
Corsair 2GB DDR XMS3200C2PT TwinX (2x1GB) CAS2 (MY-079-CS) - This week only *£127.95 + VAT*
This is value RAM and has lower timings (CAS3) so it won't be as effective as the above set, but it's still good RAM for any system.
GeIL 2GB (2x1GB) PC3200 Value Dual Channel Kit CAS3 (GE2GB3200BDC) (MY-046-GL) - £129.19 Including VAT at 17.5%