Thats sand for building foundations mate.

You want a material called Type-1 (also called MOT) its a aggregate from about 30mm down to dust, once compacted its bloody hard. It doesnt really set as it uses the fine aggregate to interlock the bigeer stuff.

Find your nearest gravel pit and order it from there, it will be cheaper than buying form the likes of Wickes and B&Q, plus they will deliver it most of the time for a small charge.

You will need to hire a wacker plate, but get it all laid out and just hire it for 1/2 a day it won't cost very much, and it wacks down pretty quick.

Hope this helps mate.