What camshaft is in it also? As if you need to replace that your looking at nearly £300.
Any turbo on it?
Also, as Bram said, Mahles on steel rods... I'm guessing it's 2.1 (86mm) they are Vauxhall Pistons, which you can get steel rods for but would probably have been a custom order as they have a small little end (21mm), but check what Vaux pistons they are as LET Pistons give too low a compression ratio on ZVH's. You need XE pistons, and the 86P serialised ones at that as those are the "squeeze cast" Pistons. Not forged, but better than standard cast.
Best way is whip the sump off and have a look at what's actually there, not what's said is there. I did when I bought my bottom end. Wouldn't hand over the cash until I'd physically checked and as they had nothing to hide they were more than happy.
I've seen a few ZVH's listed over the years claiming to run "LET" Pistons...