If immigration gave you the form to get a witness to sign it would normally mean the witness isn't required to attend. They would normally tell you or your wife. It may have changed but when we did our extension in August that form wasn't available for download. We just had our witness sign and provide a copy of their ID and house book.
What's your travel date? That visa is valid for six months from the date of issue. So if your travel date is a way off they might just be holding off issuing.
It's quite likely that the DLT office will require documents you don't have during your 10-day stay. That aside, the initial licence is only valid for two years, half of which you won't be here. Come for your holiday and worry about a licence when you move here.