Why restoration over replacement
Bristol has a huge stock of Georgian and Victorian properties where the chimney is a genuine architectural feature, and restoring the original brick or stone keeps that character rather than losing it to a generic rebuild.
What's typically involved
Restoration usually combines repointing in an appropriate mortar, selective brick or stone replacement where individual units have failed, and reinstating decorative details like corbelling that have weathered away over time.
Matching original materials
Getting a restoration right means sourcing matching brick, stone or render, and using traditional lime-based mortars on older properties rather than modern cement mixes that trap moisture in older masonry.