Well it depends on every family, all the people in the UK aren’t exactly the same 
Most the walimas in our family start around the same time. 4pm might sound insane but considering the packed schedule I think it was a good idea Our mehndis start around 6,7ish and as for the actual wedding day that really varies the earliest one would have to be 5pm lol There’s a Kashmiri wedding coming up that we’re going to i’m not sure what time that starts at 