TD5 piston rings

I'm having compression issues with my year 2000 TD5 and I wonder if anyone has any info on piston rings. My pistons are standard and probably original but after fitting new rings I'm finding a loss of compression. After a lot of head scratching (and eliminating everything else it could be) I did some investigating into the rings. I have been told that rings suitable for my original pistons are no longer available and that I need new pistons c/w compatible rings.

Is that true? I'm find it a little difficult to believe.

Could you be losing compression via injector seals or poor valve seats or stem seals.

Does compression improve with a thimble of oil in the bores? did you deglaze the bores before rebuilding?

It’s kind of academic now as it’s obvious from removing the pistons that they have been blowing past the rings. The old rings are almost identical to the new ones but there’s a small internal bevel on the top ring. I can’t see why it would affect anything but something definitely isn’t right.

On removing the pistons I discovered the Big Ends were knackered which has utterly baffled me! The old ones (242k) were like new and I only replaced them because I thought it was a good idea. New ones are totally buggered after 600 miles. I can hear all the comments already but the right shells were fitted in the right way by someone who knows what he’s doing. I’m ready to do what I was advised a while back and chuck the lot in the skip and stick an eBay runner in.