The proper solution would have been to switch to a premium rate line, and profit from it!
At £1.50/minute, you can put them into a holding queue with "All developers are currently occupied, please wait and your call will be answered shortly" played every 45 seconds. If the developer wakes up they can choose to answer, otherwise most people will hang up after a few minutes.
Assuming the average person kept on the line for 3-4 minutes, and 100 calls a month, that's £450/month revenue...
(See also: https://www.xkcd.com/1494/)
;-)