Dick,
I think you'll find that Defence does indeed take and pay for advice. Not sure of the quality of some of it though.
Defence procurement is in fact based on overseas practices, it's just that they are neither good nor appropriate for a small force like ours. Lead times of seven years for a major project are a significant part of the problem. By the time the equipment rolls out the world and technology have moved on and all the assumptions underlying the purchase are no longer valid. Combine this with a poor understanding of technical risk in the project and you have the
sea sprite.
As for accountability the project runs for so long that the people on the committees responsible have moved several times and responsibility is diluted throughout the organisation. So don't expect any heads to roll.