Wakefield Council states that there are 31 conservation areas in the Wakefield district, Castleford among them, and that Article 4 Directions apply in three of them, Heath, St Johns and Whitwood Terrace, with the properties covered set out in a separate document. The council's conservation areas page says the character of an area may include buildings, the spaces between buildings, views, paving materials, and trees and boundary features. It does not state a rule about painting.
Behind the council sits the Planning Portal, which a Castleford customer usually reads first: it states that "You do not need to apply for planning permission for repairs, maintenance or minor improvements, such as painting your house", and that in a Conservation Area, a National Park, an Area of Outstanding Natural Beauty or the Broads "you will need to apply for planning permission before cladding the outside of your house with stone, artificial stone, pebble dash, render, timber, plastic or tiles". It adds that "If you live in a listed building, you will need listed building consent for any significant works whether internal or external".
On old paintwork, HSE states that lead pigments "were widely used in paints for homes, schools, offices etc until the 1960s" and that lead "was not removed from all commonly used paint until the early 1980s". Its named controls include "leaving in place paintwork that is in good condition and / or covered by non-leaded paint", and it says "Do not over heat leaded paint by using blow lamps or gas torches". The guidance describes the paintwork it applies to and does not attach that description to any particular property.
We would explain how you check the conservation boundary, any Article 4 Direction, the listed building position and the proposed work with Wakefield Council before confirming whether permission is needed.