English and Wytch Elm (Ulmus Procera & Glabra) are just two of the elms to be commonly found in England. These are difficult trees to work with due to spiral and interlocked grain and does not split easily (firewood pile experience). Under the old manorial land system elm along with ash was not classed as "timber" and hence was not reserved to the Lord of the Manor, as was Oak, and so people were free to take these trees and use them for their own purposes. Elm does have traditional use in mills and cart building but it can also be found as building material in clusters of old buildings where either availability of same drove the population to build with this material or the quality of the elm on offer was sufficently good to substitute as building timber.
Some of the oldest buildings that I have surveyed and recorded have been made out of elm and these have now been standing in excess of 600 years.
Our 17th century granary is lined internally with hand ripped elm planks and barns frequently are found to have waney edged elm weather boarding. I doubt that sycamore would have been used extensively for building purposes as it is highly perishable but it was used for kitchen treen, draining boards, spoons because of its taint free qualities. When fully seasoned and planed to a nice finish sycamore has a beautiful luster or sheen.
Elm has to be used sensibly in buildings since it lacks the durability (fungal and insect resistance) compared with oak but I have observed from my own tests that the external perfomance of elm seems to improve as it dries and hardens so if you choose to use this material use it where it is almost always kept dry e.g. in the roof or alternatively 100% wet as in coffin boards and hand bored pipes.
Elm would not be my material of choice since it is hard to work, stringy and prone to sloping grain failures.