When I was comparing the advert to my records, I noticed that #261 & #291 were good matches - even down to the mileage. The advert said that there have been 5 owners, #261 has had 6 owners and #291 has had 5 owners - so I came down on the side of #291
That said, looking at the advert again, at the bottom of the expanded description it says that the car was registered on 7/10/2005 which matches#291, so it seems that I went the wrong way and you're right with #261
As an odd coincidence #261 and #291 both started life on a 'VX' prefix number plate so were originally registered in the Severn Valley area which happens to be Number 5's part of the country