[Bug]: Post-processing script breaking with certain calliper names

### Contact Details

jed.baker@metoffice.gov.uk

### Are there any linked Issues or Pull Requests?

#202 

### What happened?

When calliper names contain spaces (and perhaps other character) the post-processing script can't process them and crashes. This issue is for fixing the script to read in any string as a calliper name.

### Version

main

### Relevant log output

```shell

```