The brands are just the PVC. These are made in 6m lengths and sold onto factory's that cut, weld, put it all together and add handles and hinges etc.
Factory's all use different makes of locks, handles, hinges etc
I possibly should reword my previous statement to "Its all in the manufacturing, fitting, Guarantees and customer service".
Although technically Guarantees and customer service already covers that.
I personally do manufacturers guarantee + 10 years on the fitting.
Most of my suppliers are 10 years on everything (but there are so many products available now that it can vary) If a sash drops, A unit mists up, A handles breaks etc as long as it hasn't been abused (and has at least been kept clean) I will replace it free of charge for upto 10 years.
If I turn up and a part is caked in crap that has obviously caused the damage I will charge but thats rare.
The majority of company's generally do 10 years on the frames, 5 years on the glass, 1 year on fitting and moving parts so like I say its about finding a good fitting company.
Personally I don't advertise at all (van isn't even sign written) all my work is from word of mouth recommendations.
Doing the odd repair for free every now and then takes an hour or so of my time but it more than pays for itself in the free advertising I get from them telling their friends
Company's like me are quite rare nowadays though.