You might have a bit of trouble getting hold of Ichthammol ointment, unfortunately – there are some newer eczema treatments on the market now, and these tend to be more popular.
I reckon asking at a pharmacy (somewhere like Boots or Lloyd’s) is your best bet – if they’ve got any, they’ll keep it behind the counter. They might suggest an alternative product, which could be even better than the Ichthammol.
If you can’t get any Ichthammol from the pharmacy, you’ll probably have to buy it online. There’s a company called Jane’s Tote that sells Ichthammol ointment, and you can get it on eBay pretty cheaply, too.