As PeterDevon suggests, it would be worth looking at mirrorless cameras - the Canon EOS M range, the Sony A6XXX range and the Fuji X cameras all have the same size sensor (or slightly larger for the Sony and Fuji) but more compact bodies. That way you're not giving up on quality but they're easier to carry.
I have the Sony A6000, great sensor, so-so ergonomics and decent lenses can be expensive.
If I was starting again, I might consider one of the new Canon EOS M cameras - for hiking, the wide angle zoom 11-22mm lens would be great and it's apparently fantastic value for the quality. And it would probably provide the most familiar interface for you. You can get the M100 with the 15-45 kit zoom for £399 with a discount code at Wex. (I would recommend
www.camerapricebuster.co.uk for checking out deals). For another £283 you could later add the 11-22mm lens and £99 would get you an adapter to use your existing Canon lenses.
I have the TZ100 as well, which I carry alongside whichever "big" camera I'm taking on hikes. It fits in a pouch on my rucksack belt. I can definitely spot the difference in quality though.