I preferred the Rex to the Gem, I am sure the interior decoration was changed by the time I was going in the early 1960s Here is a bit of info from the website Cinema Treasures about the Rex:
The Rex - 998 seats:
Located in Hebburn, County Durham, South Tyneside, at the corner of Victoria Road West and North Farm Road. The Rex Cinema was built to replace the burnt down Theatre Royal, and opened on 5th May 1955 with Rock Hudson in “Magnificent Obsession”.

By December 1969 it was a cine/bingo operation. The Rex Cinema showed its last film John Wayne in “The Undefeated” on 26th January 1970. It became the Crown Bingo Club which continued to operate into the 1970’s.

The building has since been demolished and the Willowdene Care Home has been built on the site.

As a footnote to the information I am sure they ran Children's matinees on a Saturday for a few months after they became a bingo operation. Rock Hudson was John Wayne's co star in 'The Undefeated' so his films launched and closed the cinema, quite a unique record.