Hello Laura! I realise it's been a while since you posted this. Hope you're still there!
I've done the MVP, and the Pilgrim Marathon and I'm doing it again in a few weeks. That's how I found your post. There is one nasty hill in the Pilgrim which I think also is included in the Half Marathon. It's long and very sandy, particularly further up. That said, the Meon Valley Plod is much tougher. More long long climbs and absolutely crazy deep mud. Apart from St Martha's hill, the Pilgrim course undulates and has plenty of ups and downs and some drags, not steep but tricky when you're tired. But not as tough as the Butser Hill or much of the MVP.
I'd also say that you're in a good place. You clearly have the endurance, so you'll always get to the finish line. Glad the 5k test went well.
You should be able, I'm sure to do 1.15. Slightly more conservative - you could gun for 1.17, and in the last 2k give it your all and you'll beat your old time. The difference is between setting off at 7.30 kilometers or 7.42s. I rather expect that, rested and raring to go, 7.42 kilometers will actually feel quite comfortable on the day.
In the longer term, well, you're healthy, up and running and getting better. Keep at it with the same enthusiasm and you will go under the hour. I have no doubt about that.