Ah – sorted then.
The C2W rules are that the shop is supposed to check some sort of photo id before doing the exchange. While many don’t do this, be aware that this might restrict what you can do with it.
Either way, you’ll be the original purchases and who ever buys the bike/voucher off you will be giving up the warranty (unless it’s one of the few manufacturers who will transfer the warranty).
It’s not a bad time of year to walk into a dealer with a voucher and ask for a discounted bike though. Some might blanch at the idea of doing a discount and paying Cyclescheme admin fee/commission but it’ll depend how desperate they are.