I am 38, but not in the UK. I see business suits with skirt or trousers as a professional must have. General rule is to have 2 for every day that you would wear one in a week, so you can mix and match with blouses to create a new look for the entire month without people thinking that you were wearing the same suit all the time. And at 30 days you and repeat any of them with noone being the wiser. Navy, Charcoal, and Black are very common colors that create a classy appearance. You can then mix in full dresses in solid colors and simple patterns that are less distintive into the workweek for a more casual office appearance. Darker jeans with blouses, slacks with blouses etc...