Its could an escapee but i would hazard a guess at it being a Little Owl, listen to one using the link below and see what you think?
A Scops Owl was 'found' Old Ryhope Dene on 27th September and seen daily over the following week. Apparently local people say it's been present at least three weeks. Make me wonder whether this is Sara's bird.
Photos on Surfbirds
I think its actually not likely at all to be the same bird from the description given.
SEO do not breed in lowland Durham and are coastal passage migrants and occasionally winter at Ryhope. LEO do breed near, but all are hard to see in this area. This included Tawny, and Little.
As it so happens, if you get this forum post, Sara, would you be willing to send me an email to: email@example.com which is the official Durham Bird Club county recorder email address. As it would be interesting to know where you heard the bird if you are not happy to share here where it is.
Hm! I was more thinking along the lines that birds tend to fly around. This bird may have been elsewhere in County Durham in April and later relocated to Ryhope Dene. Perhaps a little more likely than two Scops Owl in the County - though anything is possible.