Shells and bores were inspected, they are perfect. The oil pressure was fine as long as the engine had some revs on, just from cold took 6-7 secs to build pressure, and at idle the pressure would drop off.. The engine was harldy used due to the issue, so it has not suffered at all thank god, as it is a fresh build and still running in, just glad I have got it sorted.

Still think it's very bad form to sell a crap oil pump though, they must have tested them?

The original pump had done 110,000 miles, and was pretty much perfect and would have gone again happily, but due to it being a total rebuild for big power, it made sense to stick a brand new high flow 5 bar pump in with the build.