Hello, glad to see your true service's are doing okay, hope the planting is successful and they do well for you. Back in last summer i went to see a group of five of these trees in one small area, a couple were about 8' & 10 feet' tall but others were very tall up to about 50', sadly one of the tall trees though in leaf did not look healthy at all but the others seemed okay. All five of them are direct descendents of the original wild sorb of wyre, they are thought to be planted by Dr. Cadbury, he built a chalet as a retreat to study the local flora and fauna and they are close to that chalet. i have aded some photos below for you (sadly of poor quality as batteries were low and i am a poor photographer anyway, pics of other trees were not of sufficient qualty to add), Best wishes for the future of all of your trees of all varieties.
one of the smaller true service trees in that group about 8'
the canopy of same tree
the chalet Dr. Cadbury built as a retreat
if you look closely you can just make out the tree in first pic at front of chalet (the other trees are close by but not seen in photo)