Have you lifted the carpet in the boot & checked the floor from above - particularly that the bodywork’s still as it should be along the seam below the rear light panel?
Although it does sound as if your car’s O.K. - those bumpers are designed to “give” a bit in low speed shunts. I recall that the reason for the awful rubber bumpers on MG sports cars from the mid seventies onwards was to meet new US regulations which stated that cars must be capable of withstanding an impact at up to 10 MPH without damage.
It might be as well though to ask a garage just to check it over, for peace of mind?
With a Mk1/2/2.5, check the diff carrier for any cracks. The diff carrier is designed to break to prevent damage to the drivetrain. Its not unknown for a car, following rear end repair, to be driven away and suffer diff failure.