I applied for the grant on 1st Feb, and had the voucher issued today. Just over two weeks from application to the voucher being issued. My installer did say he was amazed it was approved so quickly. So in my experience it has been a quick hassle free system. For info I'm getting a ASHP, just over 9k installed and live West Durham area. Got the full 5k on the voucher which means just over 4k upfront. Coupled with the RHI it's a no brainer imo.