Ok, thanks for the advice :) I just needed a second opinion.
Yes, I will have to take it slow when re-introducing them. But because they live in a huge cage, with Marvin on the top and phoebe at the bottom they are aware of each other. I also have them sharing the same dust and swapping round...
This isn't exactly about breeding...but I had my male chinchilla neutered exactly a month ago today. He has been kept separate from the female and he is completely healed and back to normal.
I know it is usually recommended to get same sex pairs, but I adopted these two as they already knew each...