I wouldn't bother with the unger high-flow kit. Its rubbish. I bought one, and the brush is so heavy it is very difficult to control. Also the bristles are "feathered" so hold all the dirt. It is so heavy that it has bent the small pole section I used with it. Not very well made at all.
You'd be better off with a pole from anywhere, and making your own water fed brush.
I'd estimate :
5m pole - £30
brush head - £6
hoses - £15,
fittings - £10ish.
About £61 altogether, whereas the unger Hi-flo is £100.
Silly