I always thought you had a contract at the point of offer and acceptance , not when you pay for it as Bernard is implying. So in this case the offer is Hattons advert or website and acceptance is the modeller placing an order. I haven't ordered anything from Hattons for a while having cut back dramatically because I'm at saturation point, so I'm not sure what their terms and conditions are. But you will have accepted them at the point you place order.
I sympathise with Hattons, and all other model shops, particularly the single trader. From what I see on threads on here, and a very disciplined and informative discussion over on MREmag, it looks like the response of many of us will be to cut back purchases to what we really need rather than like to have. And of course none of us really need model railways , so in the most extreme case this could be zero. So as a model shop you have to estimate demand , but in some cases Bachmann don't appear to have set the price. If its reasonable or low you are going to get inundated, if its too high , you may have stock on shelves. And as we are all cutting back, you will have less business. Add to this Hornbys reduction in retail margin and you really have a poisonous set of circumstances out there. So I understand Hattons need to change terms and conditions to cope with this. However if you have already ordered , and indeed were encouraged to do so by the offer of maintaining price as Mark (Reevesthecat in post403)suggests then they should honour that price. If theyve subsequently lost out then thats their issue, or one they should be taking up with their supplier, who presumably changed price on them. You have to make decisions in business. This is simply one of them. No one ever seems to take responsibility any more. Its always down to a set of circumstances or someone elses fault!