Protestant records don't have the kind of detail the Catholic records do. You may not find many more leads to their specific place of origin in the Canadian records
They also had a son, (James?) Harry, born in abt 1860, in Montreal, according to the 1861 Canadian Census.
I would first exhaust the records in Canada for this family and see if you can't pinpoint more specific data, in particular the birth date of the daughter, Susannah (Susan). I would then narrow down the possibilities of her birth, in the UK BMD. Then look for possible marriages in the same location a year prior to the birth. You're dealing with a common names, that can be confusing, too many possibilities, but that many give you the best leads.
You might also search the UK 1841 Census for both Henry Clarke and Ann Dixon. See if you can place both in some proximity to one another.
People recommend you order the hard copy of any UK BMD directly from the GRO.
You need a good period map to plot out locations, and lots of time, many open tabs, but this should help you narrow down the possibilities.