In my previous BMW, over the last 4 years, I would drive around for months without a valid MOT believing that other than the required safety check aspect, you just needed it to do an online road tax purchase.
So for example, if my MOT was due January, I would purchase road tax for 6/12 months in December because it would be approved. I would think nothing of it until the next time I would need road tax because then I wouldn't be approved with an expired MOT of 6/12 months.
I was never informed otherwise until very recently whilst refreshing my knowledge on the subject. Now, I've gone back and informed everyone who I gave wrong advice too about it.
What was more interesting, within those four years. I may have been stopped by police 5 times for what ever excuse they wanted to use. My details were always checked but not once was expired MOT mentioned... Maybe I was lucky. I don't know.