Hi Gary,
I don’t use Apple Pay, so don’t have the same problem, but I do have a timeout problem on my Android Phone when using a particular timer/location program, which - like PAW Radar is ‘web based’. I use an Android app called ‘Screen On’ to keep my screen live. The only one I can see on the App Store is ‘Keep Screen On’ and I have no experience of it, but at 99p it might be worth a try.
Hope this helps.
Regards
Peter