I'm sure there is but I decided not to risk breaking off the screw and maybe then having to order a new radiator.
I jacked up one side and undid a jubilee clip for a fat hose at the bottom of rad and let it drain. Then I flushed using cold water hose and tightened the jubilee clip. I then filled her up with good quality green antifreeze and topped up with tap water.
The actual mix is not that important IMHO but I suppose it depends on where you live.
Sorry for the late reply, The drain is on the left hand corner of the bottom of the radiator, remove the reservoir cap to release any pressure and facilitate draining. When refilling you should open the gold 17mm bleed bolts on the front of each cylinder to purge the air trapped inside the engine, wait for a steady stream of coolant to come out, then close.Run the engine up to operating tempature then top off the reservoir. Hope this helps.