Firstly, which British stamps do you have?
They come in values from 1p up to at least £5.00, I haven't checked but you can probably buy them for more than that as well.
If it's a portrait shaped fairly small gold one with 1st on then it's worth 46p, if it's landscape and gold with 1st on then it's worth 75p.
If it's a portrait shaped fairly small blue one with 2nd on then it's worth 36p, if it's landscape and gold with 1st on then it's worth 58p.
If it's square with a picture and 1st on it, then unless it says "Large" on, it's worth 46p.
If it's anything else then describe it on here and I'll try to identify it for you.
Next, you need to weigh the envelope which will be coming back to you. Unlike the USA, size makes no difference from the UK to overseas (unless it's ridiculously, stupidly huge, I mean really, really enormous).
Right, you're looking at Europe, so the prices you need are here
http://www.royalmail.com/portal/rm/cont ... d=53800712
If it weighs up to 40g, you'll need £1.00, up to 60g is £1.30, they're all on that table.
The prices will go up in April, if you've got the ones which say just 1st or 2nd you'll be fine, they will go up in value as well.
Hopefully this has cleared up your question for you.
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