In reply to pepperpot:
I think it makes a big difference how good you are at hills. Though of course how good you are at hills depends on how often you run up hills.
I struggle on the mildest of incline. 3 miles with a massive total ascent of a 120 feet last night as part of a quick longer run: I went from chatting to a complete wreck (while they continued to chat).
For the run you describe, I think I would be 90 seconds off flat road pace, for comparable effort.
I would suggest 9 min/mile as a sensible medium term goal for the run you describe, on 3 runs per week. I wouldn't, though, have a benchmark run that started and ended at my door. If I wanted to time myself over 4.5 miles I would have this as the middle of maybe an 8 mile run. This is maybe an age thing. If I'm running with younger people, which I seem to be doing a lot of recently, I have to do a covert couple of miles before I meet them.