It equals roughly £12.31 for a $20 hoodie and £15.39 for a $25 hoodie at the current exchange rate
Threadless are running a promotion at the moment that offers free worldwide shipping with any hoodie or "Threadless Select" branded item.
If you've never bought from Threadless before it's worth a look, they have some great original designs. The sizes of the hoodies run from XS to XXL
They have a pretty decent selection of $20 and $25 hoodies at the moment, and because of the free shipping it's worth just ordering one at a time and then you don't get stung with import tax. (Commercial consignments of £18 or less are free from customs duty and import VAT.)
When the page loads click either the $20/$25 button on the left hand side to see all the hoodies available for that price. I'm only pointing this out because for some reason the site keeps showing the t-shirt prices instead of the hoodie prices on the search page.