Replacement Double Glazing Installation

[rash_decision]

I'm looking for a bit of advice with new windows, shortly to be installed at my house.

I've had a few quotes, and recommendations, and have gone with a local company, that have been recommended and in my opinion have a very good product.

I'm signing the paperwork tomorrow afternoon, and probably paying a deposit. What is normal for a deposit here? I don't want to pay the whole amount until the job is done and I am happy, so would the cost of the windows be regarded as the deposit so the company is at least covered when they start the manufacture?

Also, what should I be looking for when they install them, to ensure they are going in properly? I'm pretty handy, so any guidance would go a long way for me to keep an eye on the installation team!