Hi,
On W/U, as worked in two serious companies using W/U for payment term, I have some other information.
The reason serious suppliers suggest customers using W/U are mainly:
1) Payment amount is not much, usually below US$1000;
2) Payment will arrive quite fast, within 1 hour, and convenient to get money;
3) Supplier / Receiver needn't to pay bank charge, saving cost, important.
So, for sample fee, supplier often suggest customer use W/U.
Meanwhile, you have to be careful if:
1) Payment amount is big, not only risky, but also bank charge will be high;
2) The supplier insists u use W/U only, no company account for option.
If you're still worried, maybe ask their company confirmation on W/U information with their company chop; if still worried, then refuse such payment term, serious supplier will give you another account.