Greenmeadows Video Ezy has no plans to close, says owner Kevin Knox.
News the building was for sale led some customers to wrongly think he was closing shop, he said.
He asked his landlord for less space in the building "and next thing I know he has got the store on the market".
He said he was unaware his fixed-term lease had expired and the business was on a month-by-month lease.
He lost his copy of the agreement in a house fire and his landlord had not informed him of its end.
"I thought when the three years came up it just rolled over," he said.
"I was under the presumption my lease ran out in March 2016.
"I sent an email to the landlord stating I would like a smaller premises - turnover has dropped since I bought the business."
Mr Knox said new-release income was 20 per cent of revenue.
Sky TV was a strong provider of new releases for many years but new internet-based video providers, such as Netflix and Lightbox, had made competition tougher.
"We still get quite a few members joining up each week, but it's not as it used to be.
"We used to hold three or four copies of a movie but we only need one or two copies now, so all of a sudden we have got more room on our shelves."
He said if the building sold and the new owner did not wish Video Ezy to have a smaller footprint, it would move to other premises.
The business was burgled last week but only a broken gaming console was taken.