Could be easier than you think.
You'll already have his full name and sort code from sending him the money.
The sort code you that you paid his money to is basically his main branch's address code. The banks list all the addresses of all their branches and their sort codes on their websites. First use the sort code to find his main branch. Even just a google search might come up trumps.
Now go to 118118.com and search for his surname and use the location as his banks main branch city/county.
Hopefully he won't live too far from his main branch. You'll then be presented with a list of surnames in that area. Phone everyone up and ask to speak to what ever his first name is, when you find him, write down his address from the 118 search.
If the search using the banks location fails to work, have you exchanged personal emails with each other? You can quite easily read the IP address from an incoming email and then put that IP address into a website which shows you it's general location. Then you can search for his name in that location again.
Once you have his address, drive to his house and take the law in your own hands.
You might be able to report it to the bank or police, but nothing much will probably happen as there is no real proof that anything happened. The only other thing you could do is to get your own back. For example, now you have his name, address and bank details including home branch, you can sign him up to direct debit services eg the RAC or AA. Both about £40 a year, and when he notices it and phones up to cancel it, he won't be able to as he won't be able to confirm his full details (eg date of birth or security questions) as you will have chosen what they are.