Johnson Matthey is leading the FTSE 100 fallers on Wednesday after the speciality chemicals group lowered the profit outlook for its largest operation, which makes pollution filters for cars and trucks.
Its share price is down 4.1% at £32.49.
Luxury fashion house Burberry is the biggest blue chip riser for a second day, up 2.9% at £23.45 after it announced strong first quarter financials on Tuesday.
The FTSE 100 is trading 0.21% lower at 7,561.52.
Housebuilding and construction group Galliford Try leads the FTSE 250, up 6.5% at 651.75p after it reaffirmed its outlook for the full year.
In May, the company announced a restructure of its construction business, impacting up to 350 jobs.
The FTSE 250 is a little lower at 19,640.35.