My experience of that vibration last year was a combination of propshaft AND VCU mount bearings. You may be able to detect which end of the propshafts, i.e. is it the VCU bearing(s) through the gear lever as you enter and pass through the rough...

are all the tyres the same manufacturer and the same tread depth would be my first call

check the propshaft union bearings, or universal joints on the propshaft that is if you still have them attached

I have an extremely good example of a ( LH Drive in France ) 2001 Freelander and have had it for many many years. It has recently developed a vibration at around 50mph, but it is not the balancing or the tracking, as have had both thoroughly...