Dear All,
Expat is fairly close with his multiplier of 14.5, which was a surprise to me as I would have expected a mutiplier based on a single commodity (a car) to be very approximate. Looking at one of the websites which has data going back to 1968, you need to use a multiplier of 13 to get from 1968 prices to 2007's price (see
http://www.safalra.com/other/cumulative-hi...l-uk-inflation/). That makes the 15 guinea special 15.75 * 13 = 204.75, or about 205 pounds at 2007 prices. Add in another 5% for the increase from 2007 to 2008 and you get a factor of 13.65, which makes the 15 guineas about 215 pounds.
So 14.5 may be close but a bit on the high side. I have looked at some other indices and they all seem to agree with something like 13 or so as a multiplier from 1968 to 2007.
There are some interesting theories about how to take into account the improvement in quality hidden in these figures. To take Expats example, how many standard features on the 2008 Focus would have either been very expensive or unobtainable technology on the 1968 Escort? This is not a subject for this forum, so I will stop there.