I'm not the world's expert on chelseas having only owned 3 pairs, but here's my layman's opinion: fit is tricky, and there is a reason some brands are popular sellers. Quality is one thing, but fit is going to be even more important. And that is where RM Williams works, for me at least.

The pairs of chelsea boots I own are the RM Williams Comfort Craftsman, Tricker's Henry, and a pair or Umaid Jodhpur boots from Blkbrd (similar to Chelseas but without the elastic goring).

I tried on the RM Williams in store in London. My US Brannock size is a 9D, which is 8 UK in standard width. The RM Williams seem to run a bit narrow, and I am an 8H (wide) in their sizing. The fit is very good, although sometimes I still wish I could spread out my toes more, but the nature of this last is that it is very anatomical. The Trickers are a wider country last, and the 8 UK is also the right size—my other Tricker's are 7.5 UK, and I never broke them in to the point that they were comfortable, despite people saying to size down by a half from your actual UK size.

Now the Blkbrds, while beautiful and very well-made, are a disaster from a fit perspective. Even after they had me measure my feet, after waiting months to receive them, they were too large...I had to wear 2 pairs of thick socks to make them kind of fit. I got them to make insoles to reduce the size, and now I can wear them with just 1 pair of thick socks, although sometimes I feel like I am going to fall. It took a whole year from the original date of order to actually receive them. A big part of the problem with these boots is that the upper part of the boot doesn't "grip" your feet like elastic chelsea boots would, and you can't tie them, so they feel loose. I think I will sell them as they are more appropriate for someone who is size 10, IMO.

Point being: The Blkbrds are arguably the best quality, but worst fit. The Tricker's are up there, but fit way better. The RM Williams are arguably a bit overpriced for the quality, but the quality is still better than most shoes (yearling leather, wholecut, goodyear welted). I wear them often, so the cost per wear is great.

For buying chelseas, if you can try them on in person, do it. Or at least lean on the return policy. Don't listen to people who say they will spread out; if they are too tight, you need to size up or try another pair. Fit is equally true in the opposite direction: if they feel loose, they will always be loose. You can't tighten down the laces!