One thing that you may wish to consider is not actually using a mast to deliver the service, if you was to install a leased line to one of the premises then you could look to distribute the connection from that property with a wireless device attached to the highest point of the property.
If all the properties are within a mile you should be able to add a wirelss receive to each property and share the connection that way.
We have done this previously in areas that are not in the rollout plans for superfast broadband & worked out quite cost effect for each household / business.
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