How much does it cost to post to Northern Ireland, from England?

how much does it cost to post to Northern Ireland, from England? Or is it the same price to post as it would be if you were posting a letter from England to somewhere else in England? because its all in the UK isn't it? Also, what if you were posting to wales or scotland from england, would that be the... show more how much does it cost to post to Northern Ireland, from England?
Or is it the same price to post as it would be if you were posting a letter from England to somewhere else in England? because its all in the UK isn't it?

Also, what if you were posting to wales or scotland from england, would that be the same price as if you were posting within England, or different?

thanks
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