Rkkwan:
CO 1E is exactly right, but no surprise there!
Also, with the specific flights ex-IAH of CO 4, 34, 10, 46, 51, 58, 93, 7 and a few others, you will often find that the check-in staff and GA will do everything they can to ensure you get flown out of IAH
if at all possible, even if you are traveling on very low fare-classes. Although I'm not
exactly saying that CO doesn't do it's best to get you out on the hundreds of
other flights as well, those listed above do, in fact, get treated a bit differently. I'm sure you probably know that, but it's always nice to hear it confirmed!
For instance if CO 4 is threatening a mechanical, a downgauge, or deteriorating weather as the evening wears on, CO does everything possible to get pax bundled onto 34 and off the ground. Same for CO 46 and 58, and even CO 10 regularly absorbs pax with onward EU connections ex-IAH that were denied boarding on 34, 4, or 46. Quite recently, my IAH - EZE flight CO 51 threatened an 8-hour delay on the ground in Houston, so CO happily packed me off on CO 93 to GRU and comped me the GRU - EZE ticket on Varig. They also did this for some Y pax traveling on very low fares. I was impressed.
CO certainly knows about the LGW weather situation and I'm just *sure* they will take care of you either within the rules (as
CO 1E points out) or within their discretion for internnational pax flying nonstop from IAH.
(I realize it doesn't seem "fair" somehow that they do this for those flights as opposed to domestic runs to MSY or ORD or whatever. . .but there is a notable difference.)
Good luck, and let us know how it works out.
LF