Apple Pay - what's the new limit? Apple Pay increased the transaction limits recently.
In the UK it used to be £30, but is now 'higher' - without a limit being mentioned in Apple's Cashless made effortless page [UK link].

Though it's not usable everywhere - stores must update their equipment to use it apparently - I've paid for the weekly shopping at Sainsbury's for a bill of over £100, which I was slightly wary it may have rejected - but it didn't.

Is there a published limit anywhere, or is it up to your bank/card supplier to enforce their own transaction limit?
There's no limitation on Apple Pay itself. The limitation comes from the terminal that the store uses. 

If you have a terminal that supports contactless cards and nothing else the limit is £30 per purchase, £100 per day, just as for a contactless card. The limit is low to avoid someone stealing your card and going on a shopping spree. And the stupid terminal doesn't realise that you have an iPhone that is much better protected than your card. 

If you have a terminal that recognises Apple Pay, that terminal would know that you are really there with your phone in your hand, with the user of the phone pressing a button, so the transaction is much safer and the limit is much higher. What the actual limit is will depend on your bank. 

Note: The difference isn't that one is unsafe and one is safe, the difference is that in the first case the terminal doesn't know it's safe, and in the second case it knows.