Did anyone have any luck finding one of those GSI H2jO filters in the UK or even a company that ships them to the UK for less than an arm and a leg?
No, I sacrificed the arm and leg and imported one.
As mentioned earlier, the fit is less than perfect. They do fit, but making coffee is going to be messy using the "inverted" method, you have to really crank up the threads to get a decent seal and they still leak a bit. Would be pretty good as a water collection pre-filter though.