Yes, it's tight, but doable. STN doesn't have the massive influx of long-haul flights in the morning that the other London airports do.

You can help your case by a) checking in online on Ryanair and b) pre-paying the checked luggage on Ryanair if you plan on taking any.

Bear in mind that if you miss your Ryanair flight check-in cut-off, expect nothing. They will not check you in a second later, and will not, as a matter of course, put you on a later flight.