Charging problem.., Alternator?? Options

[Rod]

Evening all, hope all is well with everyone! Haven't been on for a while as I've had two kids in two years and spend my days changing nappies rather than oil in the car or amplifiers!

Been ages of trouble free motoring and then today a charging problem raised it's head I hope you can help me diagnose…

Decided to take the car to London today, It's a 50km journey and it was gridlock on the motorway on the way up.. When the car was sitting in traffic the alt light started to flicker at tick over, no big deal, rev the engine and it went straight out as it does.. As the journey continued it stayed until I picked up the revs a bit more. I arrived at my destination and checked the battery connections/voltage regulator connections and all seemed fine... Left the car parked up for about four hours and on restarting it the alt light didn't go out at all.. The belt seems under tension and the fan obviously spinning so I set off on my journey home intending to get home on just the battery.. In town the light was permanently lit, very bright in fact, as if there was no circuit being completed whatsoever and then as the roads opened up and I was able to pick up some speed at about 2500 rpm the light went out and my voltmeter shot up - we have charge (IMG:style_emoticons/default/smile.gif) When slowing down however, anything below 2500 rpm brings the light back on, dimmer though not as bright as when I first started on the journey home when it was very bright.. I'm pretty certain I can hear a 'whine' at tick over which rises with revs, but once underway it's drowned out. I'm pretty confident it's the alt (the whining tells me the bearings and or brushes are having a hard time (?)

What do you guys think??

(IMG:style_emoticons/default/driving-girl.gif)

EDIT - Just going to chuck this here if I eventually need it..

http://www.914world.com/specs/alternator_replacement.php

[Spoke]

It might be the alternator; could be the voltage regulator as well.

Measure the battery voltage and the voltage on both sides of the GEN light. If the side of the GEN light opposite of the battery voltage side is low, chances are it is the alternator.