UKH

For years I have used Scarpa Vortex Walking Shoe, and usually have two pairs on the go. They always feel a tad snug, but frequently walk 12 miles in them, and have walked 23 miles in them, and never had a blister.
I now intend walking the Camino Santiago, well until I get bored, the thought of 500 miles is too much for me so I will just set off and see what happens, but I digress. I have walked around Italy for a couple of weeks, oddly for that I used a pair of Merril Accentors which worked well, but I destroyed cycling in Europe,  but I have not walked  to the extent of the Camino which is 15 to 18 miles for weeks and I expect by the end of June high temps, so this could bring foot swelling.

So my question is, anyone done anything like this, and would you consider going up maybe half a size? I think I would get something like the Merrils as they are lighter than the Scarpas.

Sounds good to me. I recently bought a pair of boots (admittedly not walking boots) slightly bigger than previously and suddenly I’m getting sore feet because my feet are slipping very slightly.

One thing I learnt from doing the Pennine Way recently was to make sure you have some decent insoles.  I relied on the ones in the new (Scarpa) boots I used and I started to get bruised feet after a week or so.  Fortunately I had some better insoles in the squash shoes I took as hut slippers and they fitted.

Thank you. Decent Insoles, now there is a thought, I shall have a look around.

Have you done longer walks in them days in a row? Might be worth experimenting with, if not. As you say, it's just shorter walks back to back, so if one 23-mile day is fine, and two or three days is fine, 22 days should still be fine, in principle.

The insole suggestion is good. Be sure they're decent supportive ones, not just squishy space-fillers

I did 180km in Denmark in a pair of soft Solomon hiking/running shoes and should have definitely gone up a 1/2 size. They’d been fine at home but ruined my little toes on the walk. 
(They also fell apart but that’s a Salomon quality problem.)

I have had good experiences with the Sorbothane ones, but you do need to be careful with how much volume they take if you have a high instep. Decathlon had a good range of cushioned ones a few years ago beyond the usual superfeet ones you see in outdoor shops (expensive and not the right fit for me).

Thank you, the foot bed thing is something I am going to look into, ASAP.