Hello again Dettori 28, Julie, Heywood and Geoff.
Good news! The birth certificate arrived today and it is the right one. There must have been a problem with it, as it has taken so long to get to me (the others I ordered arrived within a week). So you were all correct. Jonathan Dawson was born in early June 1847 to parents Joseph Dawson and Mary Lucas (so that was right too). I have got the marriage date of the family search website: 13 June 1832 in Haile, Cumberland. That's quite a few pieces of my 'jigsaw' complete - thanks to you all.
Thanks again for all of your help - you have been terrific!
Kind regards and best wishes,
Michael