Thanks @Sandman, some good insight there, appreciate your comments.
As I have many, many chunks, I think I need to look at loading and unloading these into the hash map. At the moment, they
are ALL placed into it even if you cannot see them on screen - so quite a big memory footprint and impossible to make
the world seem infinite.
1. If chunk has gone out of view, unload from hash map
2. If a chunk has come into view, load to hash map
Should only have say max of 16 chunks loaded at a time.
It is the chunks in the hash map that get rendered.
Thanks