They may well comp you directly to Platinum but there is no guarantee. Essentially if you have more than 75K EQM equivalent in some other program in the last 12 months you have a good chance, particularly if that includes some J/F travel.
What's more, AF F is not available for awards using CO miles (though you can certainly pay for it and earn Onepass miles). KL also flys IAH-AMS and can be useful. CO flies nonstop from IAH to LGW, CDG and AMS, and you can connect in EWR to 20 other European destinations. CO's BF product is not bad.
Depends what you mean by 'reasonable' and 'Y'. On full Y fares any CO elite can upgrade subject to availability at the time of ticketing. On discount Y fares this is not true - you have to wait and hope for upgrade availability within the last few days before the flight. CO flights out of IAH seem to be relatively easy to upgrade as Platinum, or as Gold if you fly outside peak hours (except to the main business destinations like LAX/SFO/EWR/CLE/NYC/BOS and a few other routes where people buy F, like LAS). I have managed 3 in 10 upgrades on BOS-IAH as gold this year (as well as 2 in 3 on other routes out of IAH and 3 in 3 on Northwest where CO elites also get complimentary upgrades). Out of EWR upgrades are much more difficult, even for Platinum, especially on transcons to LAX/SFO/SEA/... .
Not if you are not a Presidents Club member. This is the main difference between North American-based FF programs and other FF programs - elite status does not get you lounge access on domestic itineraries (upgrades instead). However, you can always buy a PC membership (under $300 per year for Platinum) or it sounds like you'll get one free with an EU address.

Glad I could be of some help!

Yes. Just register to Onepass using your UK address. Of course all snail mail (including your elite card/ credentials and free drinks/ headset coupons) will be mailed to the UK.

If you pay Y full fare yes, you get upgraded at booking time, provided space is available. If you buy cheaper economy tickets, you would be subject to CO Elite automated upgrade process (or EUA). Plats are upgraded 5 days prior to the flight, Gold 3 days and Silver the day before, provided space is available. The higher the fare, the higher chance you have to get an upgrade (e.g. a Plat elite with a expensive H fare will be upgraded before a Plat with a cheaper fare I). But some routes can be very tough, even for Plat.

No, CO elites do not get automatic access to the lounges on domestic flights. And only Plat (skyteam elite+) get lounge access when flying international coach.

But as I mentioned before, as a European Gold/ Plat elite, you would probably get a complimentary Pres. Club membership card, which would grant you access to CO PClub, NW Worldclubs and some other affiliated lounges.

Again this is a non published benefit, and conditions may vary between UK and other European countries. You might want to call CO in the UK to double check.

A little behind on this post....

First of all, of course CO is THE one to go with.

Although it seems much more appealing to retain Europe address to get some other benefits US members won't get, when requesting to get a status match, CO will know he moves to Houston and "may" require him to change to Houston address.

Yes/no?

Not necessarily. The OP does not have to explicitly state he is relocating to the US. Simply mention his new heavy travel patterns between Europe and IAH and his interest in giving his business to CO.

I have sent our mileage statements to CO about a week ago- which showns a fair bit of US travel in C with BA/UA/LH, even though none of them are through IAH. Both of us have clocked more than 150K miles with LH this year and around 25K with BA (where our qualifying periods are June to June). Have not heard anything yet.
Our main CO route would be IAH-LGW. The rest would be intra-US cheap Y travel. IAH-AMS might be useful to me as there are good KL connections to OSL.

At the moment, we hardly get any upgrades with LH or BA, so reasonable in this context would be anything above 10% :D :D That said, I have a very good transcon upgrade history with UA (3 out of 5 this year from C to F) at the time of check-in. So what I was expecting was a reasonable chance to get upgrades at the gate on the basis of our status. Anything else would be a bonus. Our CO routes would be weekend trips (Fri late evening/ Saturday morning outbound and return on Sun eve), so we might escape the paid F crowd.
Mea culpa- I forgot that US FF programs don't give automatic lounge access. That said, we have Priority Pass which allows entry to most CO and DL lounges, so even if we do not become Presidents Club members for free, we might be able to sneak in :D :D

That is precisely what I have done- I have told CO that we will have some heavy ex-IAH travel soon and would like to be comped if possible.

Just to let you guys know- CO has comped us to Gold after we sent them copies of our FF cards and statements.
Thanks again for the inputs and help.

Great! Glad the process went smoothly. Welcome to CO Onepass.

Just curious - did they mention the expiry date of your comp gold status? Will it be Feb 06 or 07?

Have not received the cards yet-there is no expiry date on my account when I log in. Hope it is until 2007, considering that it is almost end 2005.

Careful... FB Gold is E+ everywhere *except in the US*, where it's mere Elite. So, make sure that Flying Blue has a European address in its books, or you'll have to get Plat in order to have E+ status.