It seems that Surrey's street lighting PFI will use Mallatite columns and WRTL Arcs and Libras fitted with remote monitoring, and that there will be 70k replacements and 19k refurbishments (lantern replacements), affecting all of the county's 89k lighting columns. The PFI will be operated by the Skanska Laing consortium, and work will start in March 2010 initially focusing on the Reigate and Banstead, Spelthorne and Guildford districts. Replacements will be street-by-street and ward-by-ward for each district, before moving onto the next district. There will be three teams doing replacements, one team for each district. So it seems that whole areas will be relit all at once. Replacements will be largely one-for-one, and as part of the remote monitoring, part night dimming will be implemented.
Here is the link to the FAQs. Note, on the page that shows the two types of lanterns being used they state "Arc" and "Iridium", when in fact they mean "Arc" and "Libra".
That Arc looks like it could have a CosmoPolis lampholder in it.