Hi,
Don't depend on one quotation... get at least 3 quotes (up to about 5) & don't always go for the cheapest option either. Ideally a recommendation from someone goes a long way & anyone you do choose to go with, ask if have done any work in your area & go take a look. Most people would be open to chat about work done before, failing that, you'll see the outside of the house(s) & can see from that.
Try to get some time lines aswell... you don't want someone taking a long time to get through the painting.. especially if you have kids etc around the place...
I would definitely not consider this reasonable. We recently got our house painted (4-double bedroom semi d) with playroom on the side - approx 1400 sq feet and the quote was 900 (we paid for paint on top of that). I had 3 quotes ranging from 1000 - 2000. This was in Dundrum in Dublin by the way.