Nice vehicle and I would say well worth £12.5K. Having said that these are never going to be as easy to shift as, say a Scorpion or Sabre, but then they are not rare or unique vehicles in the way that a Stallion is (in relative terms anyway).. Ultimately though any vehicle is only worth what someone will pay for it and this does give rise to some anomalies - just look at the rock bottom prices that Stollies make these days, and is one Scorpion really worth the same as 3 good 432's ?
Some people also like vehicles with a bit more history to them and my understanding is these were not particularly successful vehicles in service so maybe that puts some off...
Whatever you buy just make sure you enjoy it !
Cheers