Thee are several examples of good regex to join lines like this. Here is a very basic/limited example that might help:
Search: ([a-e])</p>\s*<p class="calibre2">([a-z])
Replace: \1 \2 (space between \1 and \2)
But I would recommend doing a quick search of the forum for those example regexes (try the first sticky)....they have some great stuff!
Cheers,