I wasted far too much time trying to reclaim that account, before doing what I should have done in the first place, namely set up a disposable Gmail account, changed the email address connected with the spam Twitter account to the disposable one and then deactivating it.
However, to prevent it happening again, I've set up my own Twitter account using my email address in the hope that that will prevent anyone else using that address again. I've had people try to set up Twitter accounts before using my Gmail address, but I've always had a notification asking me to confirm the address before the account is set up. This time Gmail had helpfully sent all messages in Russian to the spam folder, so either I missed it or the spammers had somehow hacked the system so the confirmation email wasn't sent.
Anyway, I've always found Twitter to be a total timesink in the past so it remains to be seen whether I will actually use it. But I will be watching it like a hawk for dodgy activity!