Wow, what a car crash of a thread… I’d suggest you visit a decent outdoors shop and tell them what you’re actually planning on doing / aspiring to and have a think. Somewhere like Outside in Hathersage rather than a London-based chain.
Modern flexi crampons with the cradle-type plastic fittings will work on quite flexible boots for walking and won’t break ime. They won’t, however, allow you to front point, but for walking – yes, even including the extreme horrors of the Devil’s Kitchen path – they will do fine and will probably work with your current boots.
What three season boots won’t do, which proper winter ones will, is kick steps into hard snowpacks / nevé, which will save you time on easier ground and be quicker than using crampons in some circumstances.
For walking boots get crampons with straps,
You’ll be lucky if you can find crampons with straps, you want the cradle-type attachments, Grivel calls their’s New Classic, but everyone pretty much uses them now. Much faster and easier than classic straps and don’t cut off your circulation.
This is indeed like going back to the 80s… things have changed a little since then 😉