If you think other drivers have to move lanes on a motorway because you are tailgating them in a cruising lane, perhaps it's you who shouldn't be on the road. Don't tailgate them, overtake when it's safe to do so.
If you think you have to move lanes because you're being tailgated in a cruising lane, perhaps it's you who shouldn't be on the road. Don't be harassed into making a manoeuvre that you otherwise wouldn't make because another driver is aggressive, it's very dangerous to let the man or woman behind the wheel behind you control your driving behaviour, you need to be in control.
Also, if you don't know that the minimum speed on a motorway is 30mph so 45mph is deemed legal and safe (otherwise the minimum speed limit would be changed), again, perhaps it's you who shouldn't be on the road.
There is no law that says you have to overtake slow driving lorries on a motorway, if you want to overtake slow traffic you're entitled to when it's safe to do so, but you are not entitled to harass other drivers into doing so. It's a projection of aggression to say that people who slow down to deal with a tailgater are doing it to wind up the tailgater. They're doing it because that's the safest thing to do.
Don't tailgate and don't make excuses for tailgating, it's dangerous, anti-social driving behaviour, especially on a motorway in the cruising lane where there are 2 overtaking lanes of which to take advantage.