Our address is in the form "Flat X/Y, ZZ Street St".
Given that address, which part of it do you think they're expecting when they ask for "Street Address" ?
Street Number ?
Street Name ?
House Name ?
House Number ?
Flat Number ?
(and other variations)
I've seen all of those in various combinations on forms, and it still confuses me. And they never give examples or explanations. Normally things work out, but I did encounter one site (purelygadgets) where I simply could not enter my address in a way that it thought was valid, which also produced a valid postal address for me.