Hi Susan -
Personally I'd describe the countryside as 'rolling' as opposed to to hilly. That describes much of the English countryside. The Cotswolds Way, to our minds at least, seems to climb and descend the escarpment several times in the course of the day and even though the climbs are not enormous, doing several in a day becomes tiring!
As for the experience, well, we've done plenty of national trails both at home and abroad and no two are alike - it depends on the events that occur that are unplanned, things that you can't possibly pre-plan or arrange. For instance, on the Cotswold Way we delayed our arrival to our accommodation in Winchcombe to chat with a farmer who was training or practicing herding sheep round a field with his sheepdog, probably for future competitions. It was a lovely summer evening so we lingered in the sun to chat for a bit, but when we finally dawdled into Wincombe, by the time we'd got settled in, we couldn't find anywhere in the local pubs and restaurants to get a meal. In the end we ended up sat on the back steps of our B&B with Chinese take out food. Sounds like a disaster, but it's the meal I most remember!
As for places I didn't care for on the trail, well, let's just say that J K Rowling didn't call Harry Potters dreadful foster family 'Dursley' for nothing! It may well have improved since our visit which was a while ago. We stayed at a pub there too which I won't name because things will almost certainly have changed since our visit, but it was merely satisfactory (it sold beer which was a major plus point) but it didn't make us want to linger the following morning.
In complete contrast, Painswick I recall as a complete delight. And Chipping Camden and Broadway. Oh yes, and the other major thing I recall about the trip was that my right arch collapsed which I didn't get diagnosed until I returned home. I did wonder why my right foot ached rather more than usual though!
Hope you have a great and memorable trip!
Ian