I obtained this ISO Ultimate Blitz Basic v2.1 (1997)(Acid Software).iso which is available from a number of sources. This is the most complete version of Blitz Basic that was officially released.
Unfortunately the installer is broken - there is a replacement installer available on Aminet which resolves these issues - https://aminet.net/package/dev/blitz/ubbinstall
To mount the ISO on the Amiga without burning it I used DiskImageGui.
DiskImageGUI comes supplied with a CD file system AmiCDFS, but OS 3.1.4+ provides it’s own CD file system, CDFileSystem and if that is available it doesn’t copy amicdfs to L:.
Unfortunately CDFileSystem does not work well with this ISO / the Blitz Basic installer - the protect bits (i.e. permissions of the files) on the mounted ISO are not writable - this causes issues when the installer copies the files to your hard disc, and attempts to overwrite them.
To resolve this, copy the amicdfs provided with DiskImageGui to L: - DiskImageGui will then use it when it creates mountfiles.
Using amicdfs, the files on the mounted ISO have rwed permissions set, and the ubbinstall installer then works correctly!