According to Royal Mail it starts at 56p - see attached link for additional info
about 2-6 weeks
i have sent a letter to the UK, and it takes 2 stamps.
$1.20 is the rate in December, 2015.
67-89 cent
67-89 cent
According to Canada Post's site, which I just looked up, it is $0.52.
That will depend on where in the world you are sending it from, which you have not stated. Rates differ in each country and rates change all the time. Your local post office will give you rates at the current time.
it cost $2.40 to post a standard letter from new zealand to the us.(nz$)
According to the US Post office, it's .85c
To ensure that the correct postage is paid, take the letter to a post office.
i send postcode of uk in kohat
It all depends on the size and location you are sending it to/from. To get a good estimate on the price, go to the United States Post Office Price Caculator on their website. Hope this helps!