Most of the companies that I have used are pretty relaxed about the duration that the scaffolding will be required for.
Smaller one man bands might need to charge a pro rata rate because they have fewer poles and boards.
A mate of mine is a brick pointer, he often has scaffolding up for months and doesn't pay any extra, primarily because he uses the company all year long.
Try to get recommendations from other tradesmen. A couple of years ago, I needed a single lift. The company I wanted to use was too busy. I googled scaffold companies. .The first result was about £650 ex VAT. I asked a plasterer in my local pub and he gave me a small scaffolder's number. £250 for cash, but on the understanding that I would only have it for 10 days.