We used Crystal Windows. The jobs was OK but the company's attitude let a lot to desire. After we had our burglary, we had to replace all our glass windows downstairs with special laminated glass, as suggested by police. The Insurance company gave us the name of the glaziers. The double glazing glass provided by Crystal Window let us down. We also had to deal with a lot of dust after the job was over. They cut the UPVC indoors and for weeks we found debris everywhere. We also were not so happy with their quotes. We had a reasonable initial quote, but did not go along with it soon as we were in the process of having more quotes from other suppliers (some of them really sharks!). Then their manager called and his quote was completely different from his reps. He stated that the windows needed extra pilons etc..At the end our window glass panes were smaller. If I moved anywhere else, I will think twice to call them again.
If you live downstairs, get laminated glass for the window. It is not more expensive than the toughened one but is approved by insurance companies.