I doubt whether you'd get a blood test done at short notice tigwig. It's mostly left up to practice nurses to do that job now, and not all surgeries have one there every day. Even if yours has, i imagine you'd have to make an appointment and move along the queue like everyone else - unless you went privately.
Best bet's to do another home pregnancy test, or take a sample into a chemist's. You'll get a definite result from them in about an hour, depending on how busy they are.