Annoying but potentially helpful to cap the losses on an e-voucher to 20% of value..
Book BA Hol. Pay with e-vouchers + small cash element with current CC. E-vouchers refunded to original form of payment in full.. Cancel holiday. Receive 80% of holiday value to current CC. Net loss = only the 20% BA Hols cancellation fee. Probably a far better option than the Ebay lottery for someone with absolutely no use for the vouchers.