read the voucher - is it a budget travel voucher meaning it may only be for use against the purchase of a budget travel package, or is it a budget travel shop voucher for use against purchasing any product that a budget travel shop sells.
Most vouchers have restrictions that should be clearly stated .
In any event use it soon as, in the event of a financial collapse that could strike Budget along with any tour operator this year, you'll lose your money -whereas if you actually purchased a holiday or flight and the company went broke you'd be refunded by the Government. There is no refund scheme for the purchase of vouchers.