How do you stick Porcelein Floor Tiles on to Vinyl Floor Tiles?

i went to b & q yesterday as i wanted to buy some porcelein floor tiles for my kitchen.But after waiting for some istance the man who worked there said you can only use this type of grout to stick them onto concrete floor.As the people who lived before me had left the vinyl tiles underneath they have been on for many years and wont come up.the only other adhesive they had was a �34.99 packet that you have to mix yourself.Is there any way you can stick the porcelein tiles onto the vinyl tiles without having to pay that much and already mixed.