I had a couple of Vauxhalls in for an average of 6 months at the back end of last year.
2011 Insignia 1.8 Petrol, 27k, FULL VX HISTORY, Lovely car in dark blue. Took 8 months to sell, dropped from £6290 to £5890 to £5500 to £5290. Put it back up to £5800 and it sold within 6 days. Still made a slight profit on the books but guess taking into account storage and advertising its a loss.
2010 Astra 2,0 CDTi SRi 157 BHP 56k. Heated seats. FULL HISTORY 5 stamps at VX, On the face of it a desirable car I thought. Took 5 months or so to shift, had interest at first then died a death. Guy comes says its easy best one he's seen and buys it with no test drive.
No rhyme or reason sometimes so my message is don't panic. Both those cars sold within 3 days of each other after being in stock the time listed. Both customers were delighted with their cars (literally).