Those London types use Sputniks because they are (kind of) available in 48h. From what I know, they are not great quality, it's just the number of spokes which make them strong.
If you are limited to 700c and 32h, look for a deep-v rim, which will allow you to build to a higher spoke tension. Welded rims are stronger than pinned ones, but they cost a lot more too.
Those London types use Sputniks because they are (kind of) available in 48h. From what I know, they are not great quality, it's just the number of spokes which make them strong.
If you are limited to 700c and 32h, look for a deep-v rim, which will allow you to build to a higher spoke tension. Welded rims are stronger than pinned ones, but they cost a lot more too.