Odd fuel pump type noise

[nobbles]

Just recently the fuel pump on my S2 has continued wurring/buzzing. Normally when you turn the ignition it kicks in then once the engine is ticking over is no longer audible. Recently it has carried on wurring for a good few minutes. It doesn't do it all the time but it sounds as if it is not doing it any good. Has anybody else had this problem, it has been about 85 degrees outside and very humid if that has any impact...