Associate
Depends a bit; OU science degrees lack the practical elements that traditional degrees have, for example. However, in general, they're pretty highly respected. Not as much as, say, a degree from Oxford or UCL, of course but they'll be more highly rated than one from De Montford University, say. And you get the odd numpty who think they're "not a proper degree" out there, still.
Overall, they compare well with a degree from an upper mid-tier university.
I see no proof or substantiation anywhere that makes the OU an 'upper mid-tier' university. Where's the data? How better than De Montfort, for example?