Clematis roots are very thick and felshy and go deep down. It will be very difficult to move a mature plant without damaging the roots.
Half of my clematis struggled to flower well this year and I put it down to a long, cold, wet spring which made them late to get going followed by a baking hot summer. I think yours will be fine next year if given a good thick mulch of well rotted manure or garden compost any time now when the ground is wet but not frozen and another next spring when growth starts and you prune out the old stems. You can then also apply some slow release clematis feed and a liquid tonic of rose or tomato fertiliser.
If we have another hot dry spell, just give it a good drink - at least a gallon /5litres a time - a couple of times a week.