Always remove the leading zero for international calls. For the number above: 011 44 345 60 88 300 However if 0345 is one of those cost saving numbers, you may have trouble calling it from abroad.
Try this as an alternative number - +44 1443 222 111 Replace '+44' with whatever it is you have to dial on a landline... on mobiles it's always been just '+44' for me...