Does anyone know if there are any cheap deals for Eurostar to Paris, or do you have to book loads in advance? I've been looking at the Eurostar main site but it seems so expensive!

I don't think you can get last minute deals with Eurostar, I've always booked 2-3 months in advance and have managed to get prety good prices. It can also depend on the day you travel (during the week is cheaper than at the weekend)