http://www.mcvuk.com/news/read/ps4-has-sold-over-250k-ps4s-in-the-uk/0125169
PS4 seems to have sold around 250 K in 48 hours vs 150 K for XB1. For now, this implies a 38%-62% division between XB1 and PS4. My original estimates for NA and EU were...
EU
XB1 : 15-25 %
PS4 : 75-85%
NA
XB1 : 35-45%
PS4 : 55-65%
I didn't have any specific estimate for UK alone but it sure is expected to have market shares between NA and EU, closer to English speaking NA. So the current 48 hours split, 38%-62% tends to make sense, resembling the NA market, though a bit closer to EU. To be more specific, I am guessing the XB1 share in UK may either go up a bit (around 40%) or somewhat diminish, mimicking EU; but either way, the XB1 share will be consistently below NA and above EU average.
Playstation 5 vs XBox Series Market Share Estimates
Regional Analysis (only MS and Sony Consoles)
Europe => XB1 : 23-24 % vs PS4 : 76-77%
N. America => XB1 : 49-52% vs PS4 : 48-51%
Global => XB1 : 32-34% vs PS4 : 66-68%