I am a solicitor in a Scotland and will help you with this. Why does he not want the money?
You can do one of two things: 1. Leave the money in a separate bank account and tell him when he is ready to take the money you will transfer it. Or 2. Tell him if he doesn't provide details where the money can be sent you will send it to the QLTR office in Edinburgh where all money goes in respect of beneficiaries who can't be traced. He would then have to go through a tortuous procedure to reclaim the money from the state. I hope that helps. Please leave a positive rating so that I am credited for my time. See QLTR.gov.uk
There is no time limit on QLTR. There is a 20 year time limit otherwise. Thereafter the legacy would revert to the estate.