I recently purchased the Clarks Mariella Busby Chelsea boots http://www.clarkscanada.com/product/926103983/ and wanted to give you an update/review on them in case anyone is interested.
First of all sizing: I would say they run a half size small. I normally wear a 6.5 and purchased these in a 7. They accommodate a medium weight sock comfortably. I have high volume feet with bunions on both and require a medium width bordering on wide toe box. These fit brilliantly right out of the box.
Comfort: an 11 out of 10! They have this particular footbed that is incredibly comfortable while still be very supportive. I wore these the entire day Friday (first wearing) and had no rubbing, pinching, discomfort of any sort. I wore them again Saturday to the clinic, pharmacy and grocery shopping which involved a fair bit of brisk walking and again, incredibly comfortable. They have a fabulous "grippy" rubber bottom so there is no sliding and you feel very stable.
Style: a very classic Chelsea boot with a small heel, beautiful quality leather and easy to slip on. They are slightly wide in the ankle when on (visible from the side only) but this makes them very comfortable for walking with no rubbing on the ankle and easy to get on and off. My only tiny complaint would be that the ankle of the boots is visible under slim ankle pants so there is a wee bit of bunching, but honestly, it's not bothersome.
Due to the comfort of these, I am now seriously considering purchasing them in the cognac color as well and these two pairs of boots would be my primary fall/winter footwear.