lk bennett vaary expensive I think
yes, I'm in birkies too (in pale blue). They feel like slippers now but because I walk on the insides of my feet, I find they work up the hard skin around my big toe iyswim. I don't think they are actually that good for long distance walking really (did a lot of that last year and my feet hurt too) although they FEEL so comfortable, you sort of feel like you could!
I have an old pair of clarks v comfortable boring sandals for lots of walking. Actually, most of my shoes are quite boring I think.