Understood! Well first off is to have the whole suspension given a thorough going over by someone who knows what to look for. Have all the bushes, drop links, top mounts etc properly checked for any abnormal wear and tear. Then if all this gets the thumbs up, have the whole car reset suspension wise with a full geometry adjustment. Tell the garage that there is instability at 110 mph and they can adjust the cars geometry accordingly.
Another thing, when the suspension has been checked also make sure that all four tyres are good and that the wheels are balanced properly.