This depends on the Wimbledon raincheck policy, designated by the All England Lawn Tennis Club (its owners). If there is a long rain delay, then you may be entitled to a degree of refund. If you have a hospitality element to your package, this can still be enjoyed on the day and would be non-refundable. Its also worth remembering that Court 1 and Centre Court have a roof, so can continue play during adverse weather conditions.