That’s the thing; quoting is a ‘fixed price’. If you then start adding extra bits without consultation with the client, it can get a little ‘messy’. Me personally, if I’ve checked everything and there’s no issues then a quote is fine. Estimates are good as they can remain (fully explained to the client) ‘fluid’ owing to any unforeseen major issues. Also, if I’m quoting, I always add a little ‘fudge factor’ on to the price to allow for little bits here and there.