"request coins" address is different to top right qr code Bitcoin wallet app (android app).

I'm familiar with how an Hierarchical Deterministic wallet generates addresses, but I'm confused by the ever changing address of "receive coins" button in the bottom left.

Literally every time I click I'm given a different address, but the qr code in top right is always the same (and informs me it will update to new address after a transaction), but the bottom left doesn't show the actual address, only qr code, and I like to save the address each time it changes so I know which wallet it's from (so later I can confirm which of my multiple wallets will receive the payment) and also go back and check I've copied it correctly etc etc.

What's going on with "receive coins" option?
On the main screen (not the request coins page), you should see a little Tag symbol up the top in the menu bar. That opens up your address book. Swipe over to the 'Your addresses' tab, and you'll see a list of all the addresses generated by the request coins page. You can give each one a label on this page too so you remember what they are for.

The app generates a new address for each payment for privacy reasons.