Petroleum Club gives you access to CDG and AMS lounges only.

If you have a layover of over 3 hours at either airport you can also ask for a refreshments voucher. In AMS this is worth €15. There are other benefits, too.

http://www.klm.com/travel/gb_en/flyi...sive/index.htm

As for whether Tullow is registered, just go through the process (giving the proper registered address when asked) and if it's in so are you. I would imagine they would be, but the easiest way to find out is to try and register.