I have a 6+ 64gb that still runs pretty well, but I am down to 1gb of storage, so to get a storage bump I need to go to 256gb in a 8+ which will set me back £949, I just can't justify that kind of money on a phone so will probably look at a S8 (which you can get for £533 brand new with trade in plan at the moment on Samsung's website, which makes it £416 pounds cheaper than the 8+ 256, will spend £20 and get a 64gb micro SD card to get 128Gb of storage) Or I will get a second hand 7+ 128.
The decision to make is whether I stay on iOS or move to Android. I like iOS I don't tinker with my phone I just want it to work and work reliably and Apple has been really good at that for me, so it's hard to make the switch (Apple replaced my iPhone 6+ just outside of warranty for dust in camera sensor for free, doubt very much that Samsung can match Apples customer service) I used Android last in 2010 on a HTC desire HD which was a awful phone and experience, got rid of that phone as soon as contract was over went to Apple and never looked back, so my Android experience has some negative memories that I am scared will repeat themselves, lag, crashes, buggy Apps, bad battery etc etc. I know Android has improved massively since then but I pretty sure Apples customer service remains second to none (and the backup system is amazing, new iPhone restore from backup everything is like it was on your old phone)
TLDR = price rises and lack of middle storage options means I am considering Android or a second hand iPhone and not the new ones.