It was all my own fault to be honest.. :)
But I should have done a few more circuits.
Which might have cleaned it out at the time..
The problem on the Commander is the radiator. transmission cooler, aircon, intercooler are all sandwiched together, even the jet wash has had a difficult time clearing it all out.. Ether way its a excuse for the teardown soon, 185k miles it needs a few bits working on. The stray bottle good idea, but way not enough water to have cleared that out..