IIRC Paderborn used to have London flights in the past when the old Eurowings served STN and LCY (and prior to that, IIRC, LGW) by way of a Eurowings minihub at DTM or FMO. Eurowings ran a few international routes by feeding an ATR42 at FMO or DTM with pax from PAD and DTM or FMO.
It is a very affluent area with many top tier German companies located there. Wort noting that PAD currently mainly relies on Lufthansa flights to/from Munich and Frankfurt that are well patronized by business travellers. Don't expect any low cost style pricing, not feasible with a Saab 2000.