Using spent potting soil for seeds

Each year I have the issue of what to do with the soil from my pots. This year everything was late. By mid November I put my hanging baskets of begonias in the greenhouse (still in leaf) & went away for a fortnight. While I was away we had a frost so on my return I squeezed the pots of dahlias in there too. By mid-December all soil was still damp but I got the corms out and took them into the garage to dry. Cleaned them off 2 days ago and they’re now snuggly in a drawer for a few months. BUT - and this is where I’d like your opinions - I tipped the soil from cleaning the corms into a sack. It’s very fine & contains a good amount of perlite.
I will now start upon the job of cleaning the dahlia tubers. However I’m thinking that I could use that soil for seed trays. After all, we’re told not to add much fertiliser etc as initially all seeds contain all the goodness they need. Has to be better than the latest peat free rubbish, & I won’t buy seed compost as I’ve had very bad experiences with it. So what do you think? (A final thing - I’m totally out of leaf mould this year so can’t use that, and another final thing - due to a couple of mishaps I scarcely fed the dahlias this summer, which is why I don’t want to leave them in pots over winter)
Thanks in advance