Get your son or someone else to send you some cash via western union. Pick it up tomorrow, top up your phone or buy a Polish sim and call Halifax yourself.
Most likely your son, or anyone else for that matter, won't get any info about your card and account.
Pps. Should have got 2nd card :(
Yes, I have two accounts and two cards with my bank. If one card doesn't work or gets stuck in an ATM whilst being abroad I still have the second card. And funds can be transferred within second from one account to the other, just in case.
And if the second doesn't work either, there is the credit card that will almost always work no matter where.
Been in similar situations way too often. When I go abroad now I have my two bank cards, my credit card and usually some spare cash (Usually dollars because you can't go wrong with it in the east) with me.