Hi, had another overheat in the beast again, the low level alarm didnt sound when we first switched her on, im wondering if the mix of antifreeze was correct maybe the header tank was frozen

we only trvelled about 3 miles and the temp went up into the red, well this morning i topped her up with 5 ltrs of neat antifreeze and bled the system, i took nher for a drive but only went about a mile when the same happened but not right up to the red, up about three quarters of the way, i suspect the head has gone again.
My wife and myself have had enough of the problems now (what with getting side swiped by a hit and run white van and still waiting for the panel to come from Japan and now this) could it be that the cooling system is patly frozen? i think once we get things sorted we will be leaving the bongo clan and sell our beloved beast, anyone know what an m reg diesel fetches at the mo?