Remove tiles to rear and sides of chimney and put to one side. Grind a 40mm chase into the course work of the chimney.
Fit a new code 4 lead apron flashing to the front of the chimney. Re-fit tiles to sides of the chimney with new aluminium soaker on every tile.
Fit new code 4 lead step or straight flashing to the sides of the chimney and dress into position. Step flashing will be cut and shaped before the fitting.