Between the Covid disruptions, Brexit*, and normal holiday backlogs, we've noticed that shipping times are often longer than we anticipate. We will absolutely do the best we can to get your packages to you as fast as possible and we will alert you to any hiccups that come up along the way. (See our shipping policy for an in-depth overview)
That said, now is absolutely the time to start shopping if you need an order to arrive by Christmas. We are looking to add a couple of other shipping options that will give you more variety. That way you can choose the best price/speed option that works for you.
*Regarding UK-specific issues, see this blog post for more details