Always look for more work - to maximise the most income out of each customer. I'm just not pushy with it - I bring the subject of additional work into casual conversation.
If I see a dirty conservatory roof I clean one panel and then I show the customer and I say "this is a service we offer and this is the standard we clan clean to" it works very effectively as they have a comparison, suggestive selling, it's the windies version of " would you like fries with that"Graham