I do really think you need to try them on. Brasher are too narrow for either me or my DH. DH has loved Berghaus for about 40 years, I love Merrels (probably about 20 years now)
I would suggest one outdoor shop, and I think Cotswold are the best overall, with knowledgeable staff (and if you are in the Ramblers, you get a decent discount!)
Buy socks first: Bridgedale are excellent.
If you absolutely feel you must shop on-line, then I would suggest that you go for the more cushioned type of fabric boot (look for waterproof Gore-tex lining). They are much more forgiving than leather boots (although they don't last as long)
And do wear them in first!
Good luck -my arthritis prevents me walking as far as I used to, but hiking has been one of my great joys for all of my life. My first mountain was in the Peaks - Mam Tor in the days when you did have to walk up it, not just park near the top!
Is there such a thing as delicious ready meals?