if u can get the diamond thermal paste also better .
its not overkill .
its beauty .
and dat AS5 is electrically conductive .
better use other option if have .

if ur in UK and the ambient temp is <15 degrees then it will be cold enough .

u might even want to consider not getting very cold cause afraid condensation can occur .

like one of d fella said, rad at bottom easier for bleeding process .

and whichever loop style u want is possible but keep in mind that the pump is exactly after the reservoir so d pump get clean water flow from d system .