The overseas thing used to happen to me regularly too. I was traveling to San Francisco regularly for work, and after the first few trips I always made sure I had at least enough in USD on me to get to the hotel, and would always try my card first thing at the airport to get them to block it as soon as possible so I could call and get it unblocked right away.
It's gotten better - now they (Barclays) have an option in the online banking to explicitly inform them when going abroad to reduce the chance of a block. It still annoys me that I have to, but at least it's a lesser nuisance than a card block.
You'd think that after the 4th or 5th attempt, though, they would start to accept that a withdrawal of a small amount at the exact same ATM at SFO would be ok. But no.
Also, if they were to call me and check without blocking my card, I'd still be annoyed, but less so. That's what really annoys me - in no cases has there been a sudden flurry of rapid transactions, and so the risk of trying to get hold of me before blocking the card is rather small. Instead they block first and tries to call afterwards.
Another pet peeve is their security system. They call you, from a number you likely won't know is Barclays unless you take care to check the number and then save it on your phone. It's just begging for a social engineering attack by obtaining phone numbers and birth dates (the only authentication used), say from a fake online survey about banking with a price, coupled with reading up fake transactions, and proceed to put them through to an "operator" to help reverse the fake fraudulent charges, and then have the operator ask them to confirm the card details "for security", which the customers are conditioned to do when initiating the call themselves.
As much as it's more convenient, you'd think their fraud department would be more security conscious and ask you to find their number of the official website or something, but I guess that'd raise the number of complaints about their frequent blocks too much.