It’s probably my most often sourced item for projects I run (I’m a project manager for a design and build company in SW London)!
Glazing is definitely that ‘how long is a piece of string?’ product because you can literally spend endless amounts of money on it.
Here are a few companies I recommend you get quotes from: Cantifix (high-end, expensive but incredibly good service and product), Maxlight (a lot more budget friendly and a very elegant product as well), Sunsquare (although more so for rooflights I don’t think I’ve used them for doors yet), or you could go with Origin doors, which are very decent and we have fitted a number of them throughout SW London. The only people I’ve Not had a great experience with is Slimline Aluminium Glazing company, very fast turnaround but the service and aftercare was a bit of a struggle, but perhaps that was just on that project!
If you have any questions, let me know!