Well, the VFS Global shipping option is pre-paid, fixed-price UPS shipping, it's just that it is offered through the VFS website instead of the UPS website. Depending on how large/heavy your package, it could be cheaper to buy the VFS shipping, or you might find it's more expensive.
- VFS offers either just the return courier service back from Sheffield, so it's up to you to get it to Sheffield, or you can do return shipping.
- You can use UPS or DHL yourself, but not FedEx, as Sheffield won't return by FedEx (they had some issues with their return waybills last year).
- Don't use USPS though as it takes longer, isn't tracked once it leaves the US and often packages will get stuck in customs, possibly for weeks, or may never arrive.
So, you have a few options:
1) Ship the package to Sheffield yourself with UPS or DHL, then use VFS Global for return shipping ($134 per application)
2) Pay for both outbound and return shipping with VFS ($216 per application). If you do this, you will need to go to a UPS store to get a UPS envelope for the documents to be mailed in.
3) Don't use VFS and just ship it yourself both ways using either UPS or DHL. You include your online UPS/DHL account number (or an international waybill create on the UPS/DHL website) with your package so they can charge your account for the return shipping when they send it back.