"I buy single, simple parts in RadioShack"

Unfortunately Tandy (formerly the UK presence of Radio Shack) is no more.
Apart from a few major cities with Maplin stores, mail-order is the only option in the vast majority of the UK. :-(

"As far as philips MCS-51 microcontrollers it is difficult to get them in the USA. You would probabaly have to go to European sales..."

But if you go to the Philips site, you will see that the USA is the only place where you can order direct online!
Here in Europe, we have to find distributors. :-(

[rant]
This is a very frustrating part of dealing with most high-tech corporations from outside the USA: they're happy enough to provide postage-paid enquiry cards in the USA, "1-800" toll-free phone numbers in the USA, etc, etc; but don't seem to think that any market outside the USA merits any of these courtesies.
With many websites, it isn't even possible to enter non-USA contact details into their web forms (they insist on a 2-letter State, a ZIP code, a US phone number, etc, etc)
[/rant]