Very hard to say actually Steve... it really does depend on the conditions and difficulty of the course.
For instance, on a road race I would generally run a 7 to 8 min/mile pace, depending on hillls, obviously the shorter the race the faster I would run, and if it were a 5k I would usually be just under the 7 min/mile pace.
However, there have been some xc and off road races in the Somerset Series which have really slowed me down considerably, such as
on 4th March this year Butleigh multi-terrain 7 miles in 01:05:05 (I ran Babcary Road Race, which was 7.50 miles in 55:34 a week before)
I ran 2 more miles than in Butleigh, in just 3 more minutes at the Crewkerne 9 mile road race in June.
In August I did the Haselbury Trail 10k in 53:47 and 3 weeks later a road 10k at Sedgemoor in 44:33. But a week later I did Burnham Beach 10k, which was off road, and a lot of it on sand, including up and down sand dunes in 44.07!
But I suppose the biggest contrast is when I ran the Ash Excellent 8 mile race (off road) in Sept in 01:03:58
A month later I got my half marathon PB of 1.35.51 at Burnham (obviously on road) but then a couple of weeks ago ran a 16 mile cross country race in Exmoor, which took me 3 times as long as the Ash 8, and over twice as long as the Burnham half, because I finished the Exmoor xc race in 3.12.28! It was very tough though.
