Also, I've just spotted this item on here in the last couple of days and it made me think of you and your thread: http://www.lovehoney.co.uk/product.cfm?p=32806 I find it to be quite nice and suitable for the occasion. But I still think that my other suggestion for the bride is the most beautiful lingerie I've seen in a while. :)
As for lingerie for her to wear under her gown, I think an underbust corset / waspie or maybe a body stocking would be the least invasive (and might actually have a practical purpose in addition to being absolutely sexy).
This one really depends on how revealing her wedding gown is, but I like how it's a sexy little extension of some innocent white stockings that she might have been planning on wearing anyway.
As for lingerie to be worn after the wedding (maybe as a surprise romantic gift!), I think something made of silk / satin / lace would be nice. I love these because while they're not traditionally white, they just exude this romantic sexiness.