An update to this - in reverse chronology...
1) Revivals: absolutely no issue here. The chap at reception asked me what flight, so I said VS5403 and he said, "Oh, the Delta flight: DL403. Welcome!"
I sought clarification: Revivals is offered to DL passengers on DL/VS codeshares into LHR T3 on an identical basis as if it were a VS flight (i.e. DL Business Elite pax have access regardless of their loyalty programme if any; if you are VS Au, you have access regardless of cabin on the DL flight).
2) DL Business Elite (I'll try and find time to write a full trip report, but essentially it's the same as this one I did before):
http://v-flyer.com/forum/index.php?f=21 ... =viewtopic. But a few things to add: I think the menu is definitely better than VS UC (especially if you like things like smoked ribs, created by Manhattan restaurant Blue Smoke). A smaller but better wine selection (with a very good 2007 Margaux and very nice Moscatel if you like sweet wines). And then there's the Pol Roger brut...
Also: THEY LET YOU SLEEP (as in I was out-to-the-world, flat-bed, duvet-thing, pillow etc, full-on snoring away, missing breakfast - upon my request) until you're about five minutes from landing.
3) Multi-lounging: I enjoyed the fabulous JFK Clubhouse (and I met Sharma who is responsible for the delicious Guyanese chicken curry on the menu there). Haircut, massage, cocktails, meal etc.
Now the VS CH is on the 'A' side of JFK Terminal 4. DL planes leave from the 'B' side. I was told to allow 15 minutes. Well it took me five, so I thought I'd visit the DL Sky Club.
The sign says this is DL's 'flagship' lounge. Well, it's huge. It's bigger than Virgin's LHR CH for sure. But it has the usual generic, brightly lit, corporate feel.
One major bonus, though: the fabulous roof deck. I took my Bloody Mary (which I find is the best - free - thing on offer in DL Sky Clubs) up to the roof and enjoyed having a drink with he lovely view. I wish the LHR CH would let you take a drink onto the roof deck.
Conclusion: DL Business Elite with all the VS perks (Clubhouse & Revivals, identical miles and tier points - and the TPs post as VS TPs, not as partner TPs, thus counting for Lifetime Gold) is an extremely good product.
Travelling in a couple or a group, on holiday etc, I'll pick VS UC every time for the 'extra' & fun feel. On the business, where I need to sleep, or if travelling solo, I'd say I might be leaning more toward DL BE (but the VS perks are a huge part of this).
And if you just fancy visiting two lounges before departure, well...