If I try to buy one it says delivery 'estimated by 14th May', so I would guess the lower priced batch isn't actually in their possession yet, so if they're offering to price match this newer price but you're not going to have to wait over 2 weeks for delivery i'd just take them up on the offer.
Honestly it all ended well! They have agreed to refund me the difference when it gets delivered...Which is now Friday instead of Saturday and also they have given me a £10 credit on my account.