Grrrr.
I use a Buddy wing :P
They might be cheap compared to other wings, but that's because they're not total rip-offs. They're every bit as bulletproof as the Buddy jackets. Plus they can be used for single with no adaptor. £150 gets you a wing ready for single cylinder use from Buddy, compared to the £250 OMS would set you back.
And then £40 for a Combro plate and a few pennies for a brass eyelet kit gets you ready for twin 7s, cos that's exactly what I did
Why do you want the alu plate? Steel takes lead off your belt, alu doesn't. I'd only buy an alu plate if I were heading somewhere tropical, steel is better in UK conditions.
Which OMS wing? You don't need their mega-lift ones for a single or twin 7s..
You didn't mention a harness. Would you be putting that together yourself or buying one? Be aware that the OMS harness (in addition to being more expensive than a DIY and having a multitude of things you really don't need on it) only has a narrow crotch strap - I've used narrow webbing before, and it was painful. Soft 2" webbing is much nicer. And it's even more of a consideration if you're planning on buying a 100lb wing, as the pressure will be greater... tho I must confess I don't know how much of a problem that is for a lady