G'day and welcome hellbent. Sounds like everything is fine, especially if you are able to maintain 18 degrees or thereabouts. Just leave it sit for a few more days as you'll probably get a bit more of a drop in gravity out of it yet. Leaving your wort particularly at those relatively cool temps won't hurt it, in fact it will improve it up to a point. If you haven't got an extra fermenter to rack into then I'd reccommend leaving it up to two weeks in primary whilever the temps are that reasonable. If things warm up much above 24 and your gravity is 1010 or under then I'd probably bottle. John Palmer reccommends in his book (www.howtobrew.com) to leave in primary at reasonable temps for about a week after you think it has finished fermenting if you aren't racking to help clear the beer and to let your yeast clean itself up. Helps minimise that 'homebrewy' flavour. It is better again if you can rack, but don't panic too much in what I understand of your case unless it gets hot, or unless it is past the 2 week stage for a standard ale kit.
Hope that helps and good luck,
Shawn.