For UK market, check out jobserve.co.uk.
From what I've seen there, the rates for a typical strong dev are about the same in the Java and the web scripting languages worlds (js/node, ruby). However, for rare and/or exceptional experience, pay in the Java world can skyrocket. Also, finance is hiring mostly Java/.net/c++ guys, and their rates are much higher than what everybody else is willing to pay.