Is there a rule of thumb for knowing the reading of a number when it is written in western numerals, and is followed by a loaned counter-word?

For example, how would you pronounce the "1" in `１セット`? My first thought it to say `「いっセット」`, but as far as I know it could just as easily be `「ひとセット」` or `「いちセット」`. The [Wikipedia article](http://en.wikipedia.org/wiki/Japanese_counter_word) does not cover loan-word counters, and I cannot find anything on this topic.