Sorry - grandparents and great-grandparents. Please may we have an 'edit' facility?

As several correspondents have said, the 'ize' spelling is the traditional British form. That is the spelling that our grandparents and grandparents used. The Americans have simply retained that traditional form. Going on about this is simply another boring example of anti-Americanism.

That great hunter Teddy Roosevelt - after whom the teddy bear was named - spelled the word 'grisly'. I don't think there was any semantic reason to do so.
His memoir 'Ranch Life & the Hunting Trail', illustrated by Remington, is a wonderful read.

"Hot to trot?" That would be 'bedroom eyes'.

'Pony' makes 'ponies'.
'Donkey' makes 'donkeys'.
But I think it's 'grizzlies' anyway.

Perhaps 'eat' in the past tense is more standard than I allowed.
'Sayz' et al are, again, the speak-as-you-spell tendency. Pronunciation has its own integrity: it doesn't have to imitate spelling.
'Mischievious' has been around as an error for a long time now.
'Haitch' drives me nuts.

While Mr. Wilks, therefore, was thundering out, "Where are all the carpenters to walk on before King Pyrrhus?" that monarch very quietly eat his mutton, and the audience, however impatient, were obliged to entertain themselves with music in his absence.

Tom Jones Book IV Chapter I

I'm sure Fielding in Tom Jones used 'eat' (so spelled) in the past tense - presumably pronounced 'et'.

I pronounce it to rhyme with late. The 'et' pronunciation is often looked down on as uneducated (particularly in the US) but in fact it has been around for a long time and is perfectly acceptable. I heard Stephen Fry say it that way - for what that's worth. I'm intrigued that you say it has to do with age.

I'm half-Welsh, brought up in Lancashire, went to a public school and Oxford and speak RP. It's the half-tones in British life that make it so entertaining.