National Rail Travel Vouchers are issued as compensation under a Train Operating Companys Passenger's Charter, ex-gratia payments for other compensatory reasons, as goodwill gestures or for marketing purposes....
They cannot be exchanged for cash.
Its interesting that they have validity for payments on-board. If you have any, it may be worth carrying them with you on journeys just in case.Travel Vouchers (National Rail)
These are of varying values and are used for compensation under the Passenger's Charter or for marketing purposes.
They are not available for sale and must not be used for customer refunds.
They can be used in (part) payment for all tickets, including Oyster Pay As You Go top up credit.
You must not exchange these vouchers for cash nor must you give change when the value of the ticket(s) purchased is less than the value of voucher(s) tendered.
All vouchers will be endorsed with the name of the Train Company who issued the voucher, the validity of the voucher, voucher number and value.
When redeemed the receiving station/office should stamp the voucher and insert the ticket number.
Travel Vouchers may also be used to pay on-train. The ticket range which the customer can buy on the train may be restricted or subject to a penalty fare, depending on the circumstances, but the Travel Voucher can be used to pay for whatever ticket the customer is being sold on the train. Customers cannot receive any change when the value of the tickets purchased is less than the value of voucher(s) tendered.
Any other good ways to get rid of these things? I assume the OP asks is because the preference is to buy tickets on websites that offer cashback or rewards points.