Might be better finding one of those smaller independent tailors to do it though, rather than a Dry Cleaning shop, at least the chain ones anyways.
I took some stuff for repair to Johnsons and they send it all away to their repair centre, so you have to try and explain what you want done, which they then have to try and put in writing to attach to the garments. I think it took about a week and it was also pretty expensive.
I would think the small independent tailors will not only be cheaper, but will likely be able to fix/amend your stuff very quickly and they will be the person doing it, so easier to explain.