I use Filezilla because in StotskSubmitter free plan
I believe that the StockSubmitter plans restrict the number of submissions, not the number of uploads. So if you have a plan for 33 submissions a month, you can still use the system to upload 100 images, say, but it will only submit 33 of them. You can still visit the sites to do the submission manually. But that would not solve your Alamy problem - it is the submission process that marks the supertags and so you need to have enough submissions in your account to be able to do that.
Steve