Richard Sherratt wrote:

Is it OK to dump the plants into the garden waste bin or should they
go into the rubbish bin?

Probably rubbish. Really depeds on what happens to te contents of garden
waste in your locality. Mst goes into landscaping fill here.

Is it OK to plant somethihng else in the tubs or do I need to get rid
of all the dirt?

Try something other than tomatoes.