South Gloucestershire Council lists 30 conservation areas, Chipping Sodbury next to Yate among them, and on its own conservation area page says demolition of a gate, fence, wall or railing needs permission where it is "over 1 metre high next to a road, footpath or public open space or 2 metres high elsewhere". The council adds that it "may also restrict permitted development for particular classes through Article 4 Directions".
The Planning Portal sets the national rule behind every Yate job. It says you will not need to apply for planning permission to erect a new, or alter, maintain, improve or take down an existing fence, wall or gate if all of its conditions are met, among them that it is "next to a highway used by vehicles (or the footpath of such a highway) and it would not exceed one metre in height (from ground level)", or that "it would not exceed two metres in height (from ground level) if elsewhere". Where a Yate boundary already exceeds those limits, the condition is that "its height would not be increased".
Those same conditions require, at a Yate address, that "no part of the site is a listed building or within the curtilage of a listed building" and that "the right to put up or alter fences, walls and gates has not been removed by an article four direction or a planning condition". The Planning Portal adds that in a Yate conservation area "you might need permission take down a fence, wall or gate".
In Yate we would explain how you check the conservation boundary, any Article 4 direction and the proposed work before confirming whether permission is needed.