What tool do I need? #2
 

I have this head-bracket type but I’m unsure what tool or tool size to remove it with.

http://img8.imageshack.us/img8/4834/p2402090042.jpg

Are you trying to remove the stem or the headset? The stem, you'll need either a 4mm or 5mm allen wrench (is that what they call it in the UK? Not sure)
The headset, the top part comes off and the piece inside the frame, you'll need a headset cup remover (or a big ***** long screwdriver and a hammer)

I’m wanting to re-grease the bearings. :)

Then a 4- or 5-mm allen wrench, and maybe a 6-mm to take off the top cap. You have a threadless headset- you remove the top cap, loosen the clamp bolts, then the stem slides off the steer tube. unstack all the stuff until you get to the top bearing ring, remembering the order, then you can slide the steerer tube out of the head tube to expose the lower bearing ring.

Have fun. Keep it all clean, and use plenty of new grease.

Very good instructions:
http://parktool.com/repair/readhowto.asp?id=65

What type of headset is this or type of HB? :)

It looks like an Integrated headset. Could be zero stack but black on black is hard to pick out what it really is

Anyway of finding out, is it labelled on the head? The thing is only in my garage, two seconds to take a look. :eek:

If it's a stock headset on a production bike, knowing the make/model/year may help determine the headset details at bikepedia.com

The bike is a GT Avalanche 3.0 2009 Dual Disc MTB, though I can’t find it on bikepedia.com

You may have sealed bearings in the headset.