track cleaner.
 

On the mid cheshire line, I often see in autumn months a network rail track cleaner charging up and down the line.
Could anyone give me some info on this?

What class is it and when was it built?
Where is it kept?

I have been looking all over the place for info, but then again I am bad at looking:D.

It goes so fast through Hale station that I can never read the number.

I assume you mean the Rail Head Treatment Train (RHTT) that is used to clear leaf deposits off the track. They can be either locomotive hauled or MPV's.
There is an article with some good photos of the two types here:
http://www.scot-rail.co.uk/page/RHTT

Thanks swisstrains,
the second one looks to be right.