Can you use 1st or 2nd class stamp to post to overseas?

Question

I went to my local post office to send a postcard to France. The man there gave me a 1st and 2nd class stamp, and an airmail sticker. The thing is, I always thought that the 1st/2nd class stamps could only be used for British mail, and not for letters to other countries. Was I wrong?

Also, if you use a 1st and a 2nd class stamp together, as I just did, how do they know what class letter to treat it as?

Answer 1

Its the value paid that matters  about 60p isnt it

Answer 2

The stamps are fine. I dont't know why he gave you an air mail sticker, all mail to Europe goes by air.

Answer 3

to be on the safe side, just take the letter or what ever you are sending to the post office.  It would be a shame for your items not to get there, because you owed another penny or pence....