You are about to buy the same camera and 2 of the 3 lenses I own. I can say you will be very happy with the 550d its excellent for its price point. The kits lens is very good and in the right conditions the nifty 50 can be too. My experience with the 50mm is mixed however, my first copy would consistently front focus when on wider apertures, I got it swapped and the new one was much better. You will also notice that when taking pictures through the view finder in lower light it will still miss focus around 20% of the time (my experience). You can improve this situation oddly by using live view, its slower but seems to be more accurate, the explanation for this behaviour is the camera uses phase detect focusing when using the view finder and contrast detect in view live mode. However, a word of caution if you are intending to use this lens wide open for low light video. It sounds like you intend to use it for video indoors, just be aware that at f1.8 and within a room the depth of field of this lens is very small (single digit cm ). This will give you a nice shallow dof with your subject in focus and everything else out, but in my experience of video the subject moves and will most likely move in and out of focus. You can of course re focus but the lens will search for a bit and the noise of the AF motor is really noticeable on the end video. I suggest you search youtube for videos of exactly this there are plenty showing the 550d in video mode focus searching, there may even be ones using the 50mm. Of course, if you get it right the video out of this camera can be stunning ( you might want to check out magic lantern firmware (google it) if you intend to do a lot of video)
My 3rd lens suggestion to complete your travel kit would be the Canon EF 70-300mm f4-5.6 IS USM. Its not as cheap as the 55-250mm kit tele but the extra is well worth it. It's not very heavy for a long tele and I love shooting with this lens I use it a lot of the time, its surprisingly good for portrait shots.
Lastly, you do have access to the members market here and there are often some good deals to be had on canon teles in there, from memory there is a 70-200mm f/4L (non IS) in there at the mo, you can't by a sharper tele than that.
Edit, oh I forgot to mention, I travel to main land China a lot and in my experience lenses are cheaper over here from the internet than they are over there (Chinese import duty is high to promote domestic product purchase). Airport duty free is pretty much the same price as high street shops which I don't understand but you will be able get a bargain if you fly to China via Hong kong.
