IMO, it can be better to get frames locally from a bricks'n'mortar shop. That way you can see how well the corner mitres match and it's up to you to get them home safely with the glass intact, not a postie (and the various depots the package will go through on its way to you) or similar delivery service.
I tend to buy frames when I see them at a good price and decent quality with Smiths, Athena, the Range (among others) often knocking them out at reasonable prices.