How much does it cost for postage of a letter from the UK?

It depends on which country you are in and how big your envelope is. The bigger the envelope the more stamps you have to put on. ( that's in the UK)

98 cents is the cost of sending an ordinary letter to most overseas destinations, including the UK from the US. To Canada the rate is only 75 cents; 79 cents to Mexico.

Airmail letters from UK to Canada10 grams 76p20 grams £1.1040 grams £1.6560 grams £2.07Correct as of 21st Dec 2011

It's 39p for a first class stamp at the moment.

It depends upon the weight of the letter. Go through the under given site for more information: http://www.postoffice.co.uk/portal/po/content1?catId=19100240&mediaId=19100242