Melksham sits in Wiltshire Council's area, and Wiltshire is the local planning authority a tree notice goes to. Government guidance on gov.uk says works to trees in a conservation area require people to notify the local planning authority, using a section 211 notice, six weeks before carrying out certain work on such trees, unless an exception applies. The same guidance says the work may go ahead before the end of the six week period if the local planning authority gives consent.
Government guidance also says a tree preservation order prohibits cutting down, topping, lopping, uprooting, wilful damage and wilful destruction without the local planning authority's written consent. That is the rule we would quote on the page, with the link beside it.
On decking the Planning Portal says it may qualify as permitted development for eligible houses, subject to all the applicable limits and restrictions, among them height, coverage and position, with further restrictions where the land is designated or the building listed. The same page says those allowances do not apply to flats or maisonettes. On front gardens the Planning Portal says planning permission will be needed for a new or replacement driveway of more than five square metres laid in traditional, impermeable surfacing that does not provide for the water to run to a permeable area.
We would explain how you check the conservation boundary, any tree preservation order, any Article 4 direction and the proposed work before confirming whether permission or notice is needed.