Hi Ged,
Like you I have been thinking of getting one but for different reasons. If its just for getting moss out of block paving joints there is a another way. As I understand from previous post I think we both have similar equipment from Tech Clean. Very seldom do I get marks which cant be shifted and particular stubborn marks I just take a little more time in removing them.
I will get a hot box soon not only for block paving but for other reasons as well.
Be Lucky
Paul