I can totally feel your pain- I used to write blogs extensively for a company that was based in the UK, one of the things that I found that helped was to run the blog through Microsoft Documents, just set the spell/grammar check to UK instead of American English. there are other little subtle nuances that are different from American to Canadian to British terminology, the one that always sounds wrong to me is that it is only here in the States that extensive use of determiners is the norm. Being so close to Canada you would think I would be used to the difference but I swear to you if I was in Toronto and I got hurt and someone said they were going to take me to hospital I would shout back" Take me to THE hospital. " I know it is picky but it sounds weird with no "the." Another thing I notice is in this region we have a very weird way of speaking. There are many phrases that sound very Canadian, no doubt from all the Hockey we love, but then there are some words that I know have come from the areas closer to Pennsylvania. If you asked my mother for some milk she would give you maalk, if you asked my co-worker about the creek he would tell you it was a crick. Half the time people are not even aware that they are saying something strange. I used the word "pronunciate" yesterday and this lady asked me if I made the word up- go figure.
Once I started studying other languages, my spelling went out the window. I'm always forgetting whether theater is re or er, because it's reversed in French.
Of course, French was a language used in England for a long time. While one of the most famous kings, Richard I, was born in England, he barely spoke a word of English. In medieval times, much of the nobility was French (Norman) and French was used in legal proceedings and documents. It's not surprising, therefore, that many present-day English words have their origins in French.
Yes, I have seen people in the USA sticking to "learnt" rather than "learned" or using double Ls in words which American spelling doesn't require more than one. However differences are more noticeable in words that meaning the same are evidently more than one letter different, such as jewellery and jewelry, or in others which spelling has nothing to do one another, like in the case of luggage for baggage.