Beware AbroadTel - I'm pretty sure it's a scam company.
Every so often it doesn't connect or keeps you holding. I've actually spent more trying to connect than I did when I simply used 18866
Well, I have used their 1p minute number to call higher rate numbers, or mobiles, and yes there are problems connecting sometimes. Just remember to dial any additional numbers in international format, ie 00 44 870...... or 00 44 (77, 78, 79) for mobile.
As for the cost, I have checked their prices, and it is indeed charged at 1p minute from landlines.
I used the service to call just dial, and it even said they were engaged!! However they don't hang up, instead they allow you to press 1, to try the same number again, or an alternative number, which means you don't pay a minimum charge or connection charge for this, and I got through on the 2nd time!!
I can't see any scam here. They correctly price the calls. The failed calls, are probably a technology issue, and they do allow you to keep trying again, if they don't connect you, and of course their loophole has allowed people to call more expensive 0871 numbers for 1p minute. instead of 10p!!