Handy hint - download the John Lewis App & add the Watch you are after to a ‘Wish List’. If you then go into your ‘Wish List’, if the Watch is already in stock at the John Lewis warehouse, the ‘Add to Basket’ option will be active. However, although you can then add the Watch to your basket, you cannot currently ‘Checkout’ (assume you will be able to ‘Checkout’ once they start taking orders, but will that be midnight, 6a.m or 8a.m? I don’t know).
Once added to your Wish List, if the Watch is in stock, you can see the current stock level. Using this method, I think that John Lewis currently have only 8 x Series 4 Nike Watches in stock, ready for sale tomorrow & the only model they have, appears to be the non cellular 40mm with Sport Band. I have attached a screen shot of a Wish List I have created, which may make what I am trying to explain clearer.
I know about this, as when the Series 2 Nike Watch was launched, I actually managed to get a Nike Watch a few days before they officially went on sale, via this method (at the time, you could add to basket via a Wishlist & checkout, but it looks like John Lewis have now closed this loophole).
Good luck with getting a Nike Watch tomorrow (whether from John Lewis, or anywhere else)