[andy]

No, despite the same name, the SIMs are on different networks and none can be ported to a different country. You could use them at roaming rates, but as you've already decided, there isn't much point as it would be fairly wasteful. Maybe you could sell or exchange them.

From the UK, you have a choice of SIMs to make calls to European landlines, USA and Canada from 3 or 4 pence a minute, such as T-mobile with the callthrough provider Yourcallworld, or IDT Mobile, Lebara or Nomi. Calls from those to European mobiles start at around 10p to 15p a minute or so, or you can explore callthrough services perhaps from VoIP providers

If you call a lot of foreign mobiles, then O2 UK has an option with 100 minutes of international calls free for a month in which you top up by £15 or more, then the credit still to spend. I look forward to trying this to Liechtenstein or somewhere even more expensive, but not yet as prepaid SIMs don't support call diversion ...

Travelling throughout Europe, the EU countries' networks have adopted the standard Eurotariff of 59 cents outgoing, 28 cents incoming or something better. Potentially cheaper deals are Vodafone Passport, or the 3 networks with cheaper tariffs anyway and free roaming on some sister networks, or O2's My Europe Extra, with a monthly fee then free incoming calls, lending it to potential use with callback services.

There are several global roaming SIMs with either free incoming calls in several countries, or with a landline number and charged call forwarding to the SIM. You'll find plenty of discussion of these on here, with problems with one or two at the moment or in the recent past

But it will still turn out cheaper to get a local SIM in quite a few of these countries, sometimes in conjunction with callthrough or callback providers, and especially as cheaper mvno providers seem to be springing up all the time.