We even saw the back of it from across the Manchester Ship Canal in one episode.
Also, another close look at last night's episode, you can see the top of the dot in the i in the ITV logo where they've covered it up with a prison sign, you can also see one of the big satellite dishes behind the gates.
It's the same in Emmerdale where the outside of the Kirkstall Road studios has been used as several different buildings, most often a hospital.
Today's second episode was a Granada Plus edit. Looks like we've got an edit that G+ never showed. They clearly had episodes edited at least this far when they closed down.
Another Granada Plus edit on today's second episode (28/3/94), this means Granada Plus would have had at least 4 weeks' worth of episodes edited and in the can at the time they closed down.
Not surprising really- it's not like they edited them the day of broadcast. IIRC it closed around November so they may have had until the end of the year sorted, perhaps a bit longer with the Christmas break in mind. Possible to there was a view that ITV3 would pick them up too, just took 14 years longer than they might have hoped.