Don't think there is any beading or glazing cassette on that door. Open the door and look on top and see if there is a piece of wood you remove. If so the glass will slide out the top but you will need to take the door off the hinges to do this.
We fit solidor and a few years ago had no issues. They then got bought by the same company that owns doorstop. Now they seem to bow and crack. We are just about to fit our first hallmark door as an alternative.
I cannot see why the fitter/supplier should take all the risks. we have done jobs totaling £10'000 with nothing up front only then to be knocked by the customer. There should be trust between both so i say a deposit is fair
If the door is not face drained and the drainage is under the lip of the cill you should have siliconed the ends of the cill and then put the end caps on otherwise the water will run to each end of the cill and in.