In your boots I would;
1 Look on the Piper owners group web board ( I believe that there are at least two Piper owners groups maybe more for specific types) beyond question someone will have had the same problem and will show you where to get a new or overhaul.
2 Do a web search on the part number there will probably be a 1/2 dozen places in the States that will sell you a replacement which will be STC'd or an oem replacement or overhaul
3 Ask Spruce,Chiefairparts,Wagaero or Central Oregon via their web sites.
My experience is dont bother trying to get it fixed in the UK the chances are the place you take it to will send it to the States anyway and you will be charged accordingly.