Sounds to me as if the only thing you lack is confidence. As long as your PhD is Computer Science related, I don't think you'll have a problem finding a place. The key thing, once you've isolated a likely university, is to put together a decent proposal.
Most university websites provide a list of people to contact informally with regards to doing a PhD. Even if you haven't had helpful experiences in the past, I'd urge to email a few, outlining who you are, what you've done and your ideas. Somewhere along the line, you will find someone who'll give helpful feedback.