It's up to the uni you apply to as to whether or not they'll accept a transfer from the OU. Chances are they might still require you to meet their initial A-Level or UCAS points requirements, as the OU has no entry requirements of their own.
Basically there's no guarantee. You'd have to make enquiries.
As for the OU's 60-120 credits thing, that depends on whether you're studying part-time or full-time. I'm with the OU studying part-time, and I'm on 60 credits a year.