Hi Womble - that's sounds a bit weird! The flight was very straightforward. The plane took off at exactly 9.45pm at Bristol and arrived in Sofia at 12.30pm, (English time). We walked to the Ibis hotel which is less than 5 minutes away and spent the night there. That cost around £38 for a double room. Very modern and very clean. They will pick you up from the airport too for free if you request it in advance. Use Trivago to make bookings.The plane was nearly full btw although there were a few empty seats at the back- not many.
So all in all, an exceptionally easy, cheap and straight forward way of getting to Bulgaria.
P.S the flight cost under £40 with 'walk on baggage' per person. Check Wizzair's website for up to date info..