Several thousand bricks!?!
Lapua may tend to outshoot Eley Tenex in your guns, but in general the Eley Tenex can't be beat. You just have to have a gun that likes Eley Tenex, and that means a tight match chamber that nicely fits the Eley Tenex. There *is* a reason that Eley absolutely dominates both the Olympics and benchrest shooting. The benchrest guys get special chambers cut in their custom barrels that match Eley ammunition very closely, and they get incredible results.
I'd hesitate very much to say that Olympic shooters are getting frustrated by bad batches. It's much more likely that, in cases like that, they didn't do proper lot testing and got a lot that doesn't match their gun very well. If you want to see how much variation there can be from lot to lot in the same gun, I've got some very recent results of a guy that went to the Eley factory's "customer range" to have them do lot testing in his gun in their testing rig, and I can send you those results to look at. All tests were done with different lots of Tenex Ultimate EPS, and they vary quite a bit from lot to lot. That variation, however, is only showing you how good of a match that lot is to that gun. That variation isn't due to quality of the lots. All lots of Tenex meet the same quality criteria that Eley has laid out in order for that lot to be called Tenex. If it doesn't meet those criteria, it isn't Tenex, and it goes into boxes with either Match or Team labels instead, depending how far out of spec it is. They've got threshold levels that must be met to be called Tenex, and if it doesn't meet those the lot then gets compared to the threshold levels for Match. If it meets those, it goes in Match boxes, and if it doesn't, it's still likely good enough to go into the Team boxes at the next rung down the ladder. So, you're not going to get a bad batch of Tenex. But you may get a lot of Tenex that your gun doesn't like. And if you can't find a lot of Tenex that your gun likes, even if you try many, many lots, then your chamber's likely too loose to get good results from match ammo.
And with high-end match ammo, nobody measures/sorts anymore. Eley (and Lapua) have advanced their manufacturing techniques to the point that there isn't any meaningful variation in their top of the line stuff to even be worth measuring. Everybody just shoots the stuff straight out of the box. This is why the price tag on them is so much higher than mid-grade and low-grade ammo. We asked for more consistent ammo, they did the work to give it to us, and charge us for that. Mid- to low-end stuff can sometimes benefit a little from measuring/sorting, but not the high-end stuff. There's just not any meaningful variation there.
edit - Here's the thread containing those Eley customer range results. The PDF file with the results from the Eley staff are at the bottom of the first page.
http://www.benchrest.com/forums/showthread.php?t=56658