Song thrush help

Hello, We live in London and for the past month have had a couple of song thrush nesting in a holly tree with brambles, the first time in over 20 years living in this house. To say we were excited would be an understatement. Last night, I heard loud bird calls just after midnight coming from the holly tree and I went out trying to scare whatever was disturbing the birds. A fox ran away, and I think it was carrying something which could have been one of the parents. The nest seemed to still be there, so I decided to check in the morning, hoping the other parent survived. Today I was woken up by the distinct cracking of a snail's shell against stone and saw one of the birds, but it didn't return to the nest. I checked the nest (which involved a tall ladder, garden gloves and really made me wonder how anything could have got up there). The nest was destroyed from one side and it was empty. I am so upset about this and really want to try and help the other bird. Would any of you know whether, if the lone bird finds another mate (could they do that in the same season?), would they return to the old nest and try to rebuild it, or would it be a good idea for me to try and buy a ready made nest and where would be the best place to put it? Also, if anyone has any experience with song thrush nests- would you point me in the right direction as to size or materials they prefer. Any help would be greatly appreciated. Thank you in advance, Debbie