For some non-US folks, in order to get Silica to work with a phone splitter, you'll need the following info (based on German standards):
TAE-F 6 (4) [i.e. a 6-slot plug with 4 contact points] to WE 6 (4) (RJ II) [i.e. the typical "western" square modem plug with 4 tines]. The numbers on the left of the equals sign are the TAE-F contact points; those on the right are their RJ II correspondents.
1a = 3
2b = 4
3W = 2
4E = 5
I bought mine in Marktkauf, and this is all clearly labeled on the back of the packaging. But be careful: there are a lot of adapters that look exactly alike though they will not work.
The UK phone plug is just a gigantic, flattened version of the RJ II (the contacts should all correspond like to like), so you can pick up an adapter at any Dixon's and use it with the RJ II/RJ II modem cable that came bundled with your Mac. Please e-mail me if you'd like a photo of the adapter just to make sure.