Hi,
I have a few 1841 census booklets from the area put out by the Dumfries and Galloway Family History Society. They list people alphabetically, (and don't specify relationships) which can make it a bit iffy to put families together.
There are a number of female Nicholas Bells in the "Annan Landward" booklet - which wouldn't be far. they include a 12 year old at 'Millside', but the head of the household looks to be a William, 37 yr old Agr Labourer. There is also a 18 year old at 'Newbie barns 8' whose father looks to be a John, age 58, farmer. There are also 25 year old and 55 year old Nicholas' - the latter the wife of John. The family includes a Mary, age 12 and several others.
If you search for the society you can probably find how to order the booklets.
My Ecclefechan area connection is to the Johnston(e) family, emigrants to Canada in the mid 1800's.
Jim