Hey lou, you said hi once when I was new here. Now I'm here to offer advice about your toilet
If you have a trustworthy local plumber, fine. S/he will be able to deal with it.
However, if you want to see if you can clear it yourself, one easy / cheap thing to try is to grab a plunger, stick it down the bog, and pump up and down like mad. That may be enough to loosen the blockage. To check it is clear after you have done your pumping, try pouring several pan fulls of water down (easier to stop than a flush in full flow).
If you have several loos in the house and more than one is blocked, the blockage probably isn't in the u-bend, but further down the waste pipe and will need rodding (it's often where two pipes come together). You can buy rodding kits from DIY shops, else pay the plumber.
Hope that helps a teensy bit.
PS - I seem to remember you're supposed to be flying on the 8th. You may want to give the airline a call, explain things have gone ape / make up a terrific excuse and see if they can reschedule / refund your ticket. You stand a better chance of achieving this the earlier you speak to them.