Its a total waste of time trying to weld any A series heads up. To weld cast iron properly you have to use Nickle rod this welds fine but is WAY Harder than the iron surrounding it causing a whole new set of problems.
If it was a 1 off 1910 Rolls Royce, it may be worth it, but it isn't, its a Mini & as Simon says, these heads are available easily and cheaply from many sources. Just get a replacement.
