Rachel,
You're using a lawyer, right? UK lawyer, so you're sending your paperwork to your lawyer in the UK who will send it on to Sheffield for you?
If so, you *may* want to hold off on biometrics (depending on what shipping service you're using, too). Since you have 5 days from biometrics to Sheffield, and you'll need some time for your biometrics sheet and paperwork to arrive to your lawyers, you'll be cutting it close.
Or do you have all of the lawyer's paperwork now, and you'll send it yourself? If so, disregard this message.
In England, both this Friday and Monday the 17th are bank (public) holidays.