18185 is more attractive in some cases as Heinz points out.(It does have a slightly higher connection charge 4p instead of 3p.)
However if you want to use 18185 from Cable or Mobile its access 020 and 0808 codes still do not work
If you are looking for cheap calls from a landline to a Intl Number
www.topupnow.co.uk is worth a look at. Now offers 17 free destinations,a lot more at a 1p.(5p connection charge applies).
www.topupnow.co.uk