Interesting thoughts from everyone - thanks!
I currently have a Galaxy A40, and battery life is better than any other phone I've had - which is not saying much as the most top-end phone I have had is an iPhone 7 from work. However, I agree with another poster who mentioned that the battery life while using eg: VR on flight mode was about 20% for a full days walk/navigation. So, no complaints there!
My main thought about going down a different route is not only about cost (although I'm thinking I can buy a handset and a SIM only deal that would cost no more than my current contract over it's 2 year span) but also that I'd like a more bomb-proof handset with great battery life for navigating in possibly tougher conditions than a day walk in Northants.
Having not experienced a "top-end" phone performance, I don't think I'd miss it - I'd be looking for performance more akin to my A40 (or better if I can) for using the few apps I do (Social Media, e-mail, phone, camera, Spotify, smart house apps, etc - no gaming or anything like that) with excellent battery life and the confidence that a wet day or an unforeseen accident isn't going to ruin the phone. I wouldn't want a massively heavy unit, but the potential bonus of a rugged unit might outweigh (no pun intended) the extra few grammes.
Xiaomi, Doogee, Ulefone, Oukitel and Blackview are all names that crop up during searches, so very interested to hear the experiences of users of any of these.
GP