For the moment, I think I'll have to reluctantly stop the update.
The update is so feverish tonight that there are literally seconds between each transaction and the shopping cart can't keep up which means that the same yarn can be bought by more than one person and I'm not happy that people are being left disappointed in thinking that they've bought yarn when someone's got to it first and it's happened on more than one occasion tonight.
I think the best and fairest way I can do it is to load the remaining yarn into the shop in batches over the next 24 to 48 hours.
I'm not sure what the long-term solution to this problem is - I may have to switch to random updates. Any suggestions more than welcome but I'm sorry I won't be able to reserve any yarn.