Icesave is a trading style of Landsbanki Islands hf in Iceland.
They have a freepost PO address of
Freepost RRBE-YYSB-EJBU,
Icesave,
PO Box 1164,
Newcastle upon Tyne,
NE99 1DG
But they are registered with the FSA and Companies House as:
Beaufort House,
15 St Botolph Street,
London,
EC3A 7QR
A 192.com search, BT DQ search, Internet Archive search returned nothing.
The press-pack (media) contact has 020 7518 3000 but the corresponding email is @heritable.co.uk.
Looking at the webaddress
www.heritable.co.uk reveals its Heritable Bank and their parent company is the same as IceSave's.
You could try the media contact number above stating that you're calling from outside the country and can't dial 0845 numbers and could they transfer you (this may not be possible) or do they have a geographical number that starts with 01 or 02 for them.
Alternatively, fill in IceAge's online contact us form and state that your outside the UK and are trying to call them but you can't dial 0845 numbers so could they be so kind to provide a geographical number beginning 01 or 02.
I'm not sure if their call centre is based in the UK or not or if its outsourced but there again the number for the media contact (above) may be them though.
Please come back and let us know how you get on.