Thanks for your reply.
Sadly, the same issue has happened to me on more than one occasion when we have sent Purchase monies to another Solicitors HSBC Bank.
Having spoken to the Solicitors at the time, they informed me that HSBC had done this on more than one previous occasion and each time, would not release the monies until their security check had been finished. Although it is no consolation to you, I have not heard or come across any other Bank that does this!
In my cases, we were meant to complete on the Friday and HSBC eventually released the monies on the Monday and the other time, HSBC held money for 5 days. Therefore, you are very much in the lap of the gods as to how quickly HSBC release the monies.
Basically, as I think you are aware, HSBC place the monies in a holding account, pending their checks, and I'm afraid there is absolutely nothing Santander can do to speed matters up. However, your Solicitor should be putting pressure on HSBC to release the funds into their client account. From your point of view, you will of course need to demand that your Solicitor pay any interest and any charges incurred by you in completing late, and it is then up to your Solicitor to recover these costs from HSBC. For what it is worth, luckily, under the terms of your Purchase Contract, you will have 7 days to complete the purchase,so not all is lost, as I would certainly hope that HSBC release the funds by tomorrow or Wednesday at the latest.
In the meantime, I am afraid you are going to just have to wait until HSBC complete their check- the infuriating thing is that HSBC do these checks randomly.
Sorry I can't be any more positive than this, but I am just letting you know the legal position.