Pilot Paul, a quick question. Have got access to a 340 and are just looking for an instructor or do you need to find an aircraft as well? If you have the aircraft then find an air taxi firm in southern UK that operates any of the Cessna 340/400 series aircraft and ask their CRE/CRI. If you need an aircraft, use the CAA's G-INFO database to track down the UK registered ones and contact the owning companies. There are N-reg 340s in the UK but I don't know how you're going to trace them.