Thanks for your enquiry.
Only if you instruct your Solicitor to hold on to the Sale proceeds can he hold onto the money, as this legally belongs to you!
If there is only going to be a week or so delay, it would be normal for the monies to be kept by your Solicitor in your client account, only because by the time he has sent the proceeds to you, you would then have to return it almost immediately.
The decision therefore rests with you and not your Solicitor, although it would be wise for your Solicitor to retain sufficient monies for your Purchase if there is only going to be a week's dely.
Please let me know if you have any further queries.