How long does money laundering checks take for exchange of contracts?

[Promise22]

So we are in a chain of 4 houses. All ready to exchange. Bottom of the chain sent money to solicitor on Thu, they have been doing the 'necessary' checks since! Can someone please enlighten me as to what is taking so long? I assumed the checks are quick. Please note that the bottom of the chain are putting in £35k so not millions of pounds that need to be tracked. 🤔 I will be moving into the property at the top of the chain and I need to line trades people up for renovation work. I just can't plan at the moment....should I worry? Has a problem been identified do you think? Or just routine checks?

Well it was a bank holiday in Scotland yesterday, is anyone using a Scottish bank?

They did the check on our funds right at the start.
But we sent money on Tuesday. Exchanged Fri.

It's all happening in England, so I doubt the delay is due to the bank holiday in Scotland. Just worried as I have undertaking to do some of the renovation work between exchange and completion, and I just can't plan now. 🤦🏻‍♀️

NatWest mortgage team are based in Scotland (or they were in 2019) so that could also be affecting things

Ok, so apparently some documents for the source of funds are still outstanding from the bottom of the chain hence the delay! Should I worry! 😧