2021 - What I did today

Today I emailed Gardener's Question Time to ask them for advice on stopping red spider mites taking over my greenhouse again next year. I've never submitted a question before, I hope it gets read out sometime!

I haven't got those but I seem to have fungus gnats all year round  turn my back and bang they are there. I also had a few tomatoes with white fly on last week...so today I've made a start on cleaning it out. It was very wet, lots of rain so I could t use the jet wash. Just scrubbed it out with soapy water and bleach. Will give it a jet wash when I can empty it. 

How often do you clean it?
Are there any ladybird/bugs etc that you can introduce to control them?