You got it!
I deleted about 3000 channels, and Kodi seems able to cope!! Need to check more, but it seems to be working.
FYI: NPVR doesn't seem to do well with bulk deleting. e.g. trying to delete 1000 channels at once either does not work or causes issues.
I had to delete them a page at a time. A boring process but ok IF you know that is what it takes.