When I was a contractor at a major bank, the standard was IE6, and movement towards IE8 was in progress (as Win7 was rolling out)... I don't know if they held at IE8 though, as most people I knew there have left, even the FTEs. It was an SPA that drove a lot of adoption/allowance to use Chrome/Firefox, so it may have well gone that direction since leaving.
The move from IE6 to IE8 has (pretty much universally in the investment banking industry in the UK) only been over the last year or so.
They are still pretty much all on XP, but new laptops are generally Windows 7 (with IE8) and I suspect Win7 will be rolling out to older standard builds (both desktop and laptop, machines old enough to not be Win7 compatible having been replaced already) as the first thing the relevant TS departments do after the Christmas/NewYear non-emergency-work freezes.
