Thunderroad

You could get lucky in London in late March/early April, but you're right that the chances are it will be cool, gray and perhaps even rainy. Still, it's a great city. I know you don't want to hop around to two different locations, but two nights at the Savoy and then two nights at the Park Hyatt Paris could be sweet. Weather in Paris likely won't be great either, but it's such a wonderful city that weather matters less there.

I imagine that Asia is too far away for a four-day trip...or maybe you could make it a longer trip and add other destinations? Both chains have hotels in Singapore and Shanghai. Singapore will be hot; Shanghai perhaps cold, though I'm not certain. Singapore is very safe and easy to navigate as everyone speaks English. The knock on it is that it's sterile, but it has some great food and enough to explore over the course of a few days. Plus you could hang out by the hotel pool. And it's easy to tack on a trip to a Thai beach from
Singapore without having to go through Bangkok.