It depends whether the persons bank you are sending to is accepting the new fast bank transfer facility that started last year.
I can transfer money from my Alliance & Leicester account to my HSBC account almost instantly.
*you can check the two banks here to see if they support it*
http://www.apacs.org.uk/sortcodechecker/index.html
Should be pretty instant then, although Alliance & Leicester's online banking is awful. The money will probably be available but won't appear on the statement straight away.
Should do, but I don't think anybody can give you a 100% definite answer. In the meantime, you could give HSBC a call and ask as the longer you leave it the less likely it will arrive in time?