Even if you don't go with us? I'd not do this. A few big problems here.

1. The overseas company will probably add links to your site. There is no real problem with adding links to your site, there are many reason to add links and search engines like links. The problem is, Google does not allow links to be added for the sole purpose of getting higher search engine rankings. There must be a useful purpose to them. If links are added solely for the purpose of search engine marketing and Google finds out? Expect a long term penalty.
2.  Overseas companies tend to gather links from irrelevant sites and get them to link to you. How much value do you think Google places on a link from a dentist, a link from a honey farm and a link from a shower head manufacturer, if you are a florist? Not much. its a waste of money to pay for such links. On that note, Google bans sites that pay for links as well!
3.  Overseas link companies, even some from Australia, add the same links to all their client sites. Google soon spots these, and records them as link farms. You are back in penalty territory.
4. These companies send out mass emails, many of which find their way to Google. Google then slaps on the penalty for link gathering.

The bottom line is, almost all our clients have tried some internet marketing and link marketing, either with an Australian business or an offshore company. They come to us, because it did not work out.

We want you to work with us, but if you choose not to?

Make sure you have a good look at the methods of your SEO company, because if they do something banned by Google, its going to make things even harder for us down the track when you contact us to fix the problem and do the job properly.