I have taken propranolol in the past, was on it for over 5 years at various dosages, suually on 160mg LA. I also noticed disturbed sleep when I was taking them, although to be honest my sleep pattern has always been very erratic.
The probable reason for its effect on sleep is it lowers melatonin production, which as most folks know is the "sleep" hormone. My suggestion in the first instance would be to take L Tryptophan just before retiring, which is a naturally occuring amino acid that boosts serotonin product and in turn nocturnal melatonin production. From the literature I've read 1-2 grams is adequate to double night time secretion of melatonin which should in turn relieve some of your problems.
Good luck!