Sad to see China Airlines move to Heathrow and like others mention, I can't help but think they will not return if permanent slots can be obtained...
It was a great alternative route, to travel to Australia and Taipei is extremely easy to transfer through (only downside was the connection was around four hours). Even though I live north of London, with Thameslink getting to LGW is a breeze and the 9pm departure slot always made the airport easy to get through as its quite quiet then.
The A350's on the route are some of the most comfortable long haul birds flying, with a beautiful cabin layout with this bamboo effect cabin walls, extemely spacious seats in all cabins and reasonably decent service/food. You could regularly get tickets in their premium economy cabin for the price other airlines would charge for econopmy.