AmE versus BrE

The differences between British English and American English are becoming more and more frustrating, especially since I've made the choice to write in British English after having spent two years in the US. When I started at UWC I was determined to keep the English form which I'd used ever since elementary school, British English. But after a while I got tired of changing neighbor to neighbour and harbor to harbour when I took notes off the black board, which gradually caused me to adopt the American form of English. For about two years now I've been writing in AmE, but decided to go back to BrE when I started my BA in English-Norwegian translation. Most of the time it works fine, but sometimes going over from realize to realise and color to colour makes me having to put an effort into remembering those changes. But that is only half of it. Changing a letter here and there is not very demanding. What causes the frustration is when words don't have the same meaning or when the words for one object are different.

Here are some examples:
In England they mostly use lorry instead of truck.
In stead of writing riding comfort you should use driving comfort.
An American ton and a British ton is not the same unit, nor is a billion the same.
One billion in the US is a thousand million and one billion in Britain is a million million.
In Britain you change the tyres of your car and not the tires.
To change almost every z to an s is also quite annoying. You shouldn't write
nationalization, but nationalisation, not realize, but realise.
If this isn't enough you have the different things describing a car. You have the boot, the bonnet and the bumper of a car in England, but in the US the car has a trunk, a hood and a fender.

I could keep on going for ever, but it doesn't really lead me anywhere. Conclusion is that I just have to learn to cope with these words, memorise (not memorize) what the differences are and be consistent sticking to one form throughout a text.
Now I just have to decide which accent to work on..