I am booked for September in a Grand Villa Bay view. I would like to have a seven seas lagoon view, a similar view that you get from the lounge. When I make the request, what Room/Villa number should I request? How far in advance do I make the request?
You are guaranteed a view of Seven Seas Lagoon if you have an MK view. Since you have a Lake View, you can still see Seven Seas Lagoon, at least from your balcony, but it will be off to your side.
work2play has a thread showing BLT rooms and views and her first post has a map showing the location of the rooms by view category. In Post #602 (see
http://www.disboards.com/showpost.php?p=34979453&postcount=602), there are photos showing the view from villa #8434, which is directly one floor below Grand Villa #8534, which is a Lake View GV. Since Seven Seas Lagoon can be seen from #8434, you should see it from #8534, or maybe #8536 and #8540 as well. But I doubt these Lake View Grand Villas will have as great a view of Seven Seas Lagoon as seen from the Top of the World Lounge.
You can request a villa at any time. All BLT Lake View GVs are either on BLT's Northern crescent or, like #8534 - #8544, its Southern crescent. If you really want to see Seven Seas Lagoon, then you should ask for a GV on BLT's southern side. However, as
work2play's thread points out, the GVs on BLTs northern crescent can see parts of the Magic Kingdom and the fireworks. The way I see it, if you have a BLT GV you are in a win-win situation no matter what villa you get.
Good luck!!!