I'd like to follow up on this now that I have some experience.
My client first tried the ordinary UK postal service, which then translates to the USA postal service when it comes to me. Well, it arrived rapidly in the USA, but the USA Customs held on to it for two whole weeks before releasing it. By the time that occurred, we had already abandoned that route and done a wire transfer. So don't do payments through ordinary postal services.
When my client moved to doing it through a wire transfer, it was for $8K. Now first of all I should never have done that. I mean, what happens if the client says he's wired it and I never received any of it, or I only receive like half of it? Sue him? Yeah, that will not work. So now I have a rule of thumb of two weeks or $2K, whichever comes first. If I've done 2 weeks worth of work, I need to get paid. If I make $2K, I need to get paid. Whichever comes first. And, if I've established a good relationship with a client, then yes, I might be flexible and get paid monthly, but very large payments with a foreign client are a tremendous risk -- especially in the PHP website building business.
Okay, so in the wire transfer, my client said he was charged $50 on his end, and by the time it transferred through all the banks to get to me, it was down about $35 less than the $8K. So, this should let you know what you might expect.
I had another client paypal me but he's in the USA. I was to be paid $75, but PayPal ate $3, leaving me with $72. (BTW, PayPal's TOS says you can't bill a higher rate to compensate for the PayPal rate.)
So I asked a guy in town who runs a Mexican restaurant here in the USA. He sends money to Mexico all the time. I asked how he does it. He says if he wants it there fast, he does a wire transfer. But if he wants it there in a week or so, then he sends it via FedEx as an ordinary check, and NEVER uses US Postal Service. He said he's NEVER had an issue either way except some occasional unexpected delay, but the money always arrives. He also says that the wire transfer fees usually only eat up about $50 out of the payment, at most, in his case.
As for risk with the wire transfer, I have a relative who works very high up in the bank I use. She said there are enough controls on wire transfers that there's no way possible anyone can yank money out of my account without me personally coming in with my driver's license and signing for it, and knowing my home telephone number and social security number.