I may not be making it too the practice day. On the way back from Walter's place tonight the Adub burst the coolant / heater hose out of the head & the air bleed valve at the thermostat (conveniently just before the BP & Maccas on Milton Rd).
Bursting the hose and valve simultaneously could just be a coincidence, however my gut feeling is that the 4AGE has blown a head gasket (micro bubbles / foam in the coolant, intermittent steam in the exhaust). If this turns out to be the case I won't have it repaired by next month.