It depends what type of mail you're sending (and the weight)...  According to the Post Office web-site, to send (for example) a 100  gramme letter by airmail-and have it d … elivered within 2-3 working  days, the cost from the UK is £8.86.Jason Harmon.t depends what type of mail you're sending (and the weight)...  According to the Post Office web-site, to send (for example) a 100  gramme letter by airmail-and have it d … elivered within 2-3 working  days, the cost from the UK is £8.86. Jason Harmon.