Hi David, "Love" in English doesn't always mean romantic love. You can say "I love my wife," but you can also say "I love ice cream," i.e. I really like it. For your example, "they loved it" means they enjoyed themselves a lot. Here, "love" means "enjoy" more than "like." Since "enjoy" is not a stative verb (it can be used in continuous constructions, and it is more of an "action" than a state), you can say that the children "loved" London because they had a good time. They really enjoyed themselves. Hope this helps!

Not necessarily. Maybe they love it now, maybe they don't. The sentence doesn't tell us whether or not they still love it. The past tense in this instance just means that they enjoyed the experience they had in the past, no more and no less. If you wanted to imply that they no longer like London, you might say "They used to love London" instead. However, using "used to" also carries the idea of something occurring over time, not just one instance. For example, "when we were children, we used to love cartoons; now that we are older, we do not".