If you are looking to replace Elm trees due to Dutch Elm disease, details of where you can source disease resistant tress are below:
An Italian clone FL493, is now sold by Frank P Matthews, https://www.frankpmatthews.com) under the reg. cv. name 'Wingham', in recognition of the village in Kent where it was extensively trialled by Dr David Herling,
www.ResistantElms.co.uk They are also selling a Dutch variety ‘Lutece’.
Peter Shallcross (email: firstname.lastname@example.org) - supply Adamuz, Fiorente, Lutece, Wingham and Ulmus laevis trees
Hilliers Nursery who are selling New Horizon. https://www.hillier.co.uk/trees/products/listings/ulmus-new-horizon/