Firstly, composite is your best bet although more expensive. The bulk of composites are made by the same manufacturer and distributed to upvc/ aluminium companies around the country. (visit a few showrooms and all will give you the same brochure).
Look for a long established firm in your area and get a price, any variable on the price is likely down to how busy they are.
I've both used and recommended in the past Micron Building Services, both myself and my family (Mum & sister) have gotten various works carried out - new doors, windows etc. and found them great. His number is 086 2713239. I've upvc too but would love one of the new composite doors ... let us know how you get on.
I got a composite door and frame etc. a year ago from Regency Windows and no problems so far. They were not cheap but a bit cheaper then the other places I tried. The difference it made in heating the house is unbelievable
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