What`s the first part of your postcode ?
ST12

Sorry for the slow reply - I don`t think Scottish Power are the REC for
that postcode area (parts of ST7 only IIRC)

You may find that tree cutting has its own department in the REC that
does cover that area, and they will trim the tree for free around the
path of the line to ensure the security of the supply - which in turn
would allow the tree to be chopped in relative safety.