I would imagine most of the stock coming in to the UK would be via sea freight to Europe rather than airfreight direct, in which case shipping time is 6-8 weeks.
Having said that, some cards have Feb/March as ETA so those cards would have to be in transit already to meet those dates.
Vast majority of GPU's are airfreighted in as of 3000 series. With the increased value of 5000 series, I doubt we'll see sea freight expect for the 5060, 5070 etc models.