I suggest:
"Harlitt�s chocolate factory, which had been employing over a thousand people, has closed down".
"It is difficult to give rules for the choice between the to-infinitive clause ... and the ing-clause." ("An A-Z of English Grammar & Usage, Geoffrey Leech, et al, page 234, 2001.")
"But avoid using two to-infinitives or two ing forms one after the other." Page 235.
Examples|: "I would like to begin studying as soon as possible."
to study X
"They are beginning to improve the road."
improving
X
In my sentence I have used the Past Perfect Progressive/Continuous Tense.
I see it as "An action began in the past and was continued until another action occurred". ("Using Tenses in English: Past, Present, Future. Manik Josh, page 62, 2014".)
Example: "She had been living in Washington for four years before she left for Paris".
I hope that this helps.
Les Douglas
