Hodson It looks like there are now CentOS7-compatible releases for Swift, so you can download and install it in your shell user home directory like this:
cd ~
mkdir ~/opt
wget https://swift.org/builds/development/centos7/swift-DEVELOPMENT-SNAPSHOT-2020-10-15-a/swift-DEVELOPMENT-SNAPSHOT-2020-10-15-a-centos7.tar.gz
tar zxf swift-DEVELOPMENT-SNAPSHOT-2020-10-15-a-centos7.tar.gz
mv swift-DEVELOPMENT-SNAPSHOT-2020-10-15-a-centos7/* ~/opt/
export PATH=$HOME/opt/usr/bin:$PATH
export LD_LIBRARY_PATH=$HOME/opt/usr/lib
Hope this helps!