A motorway question...

[KindergartenKop]

Am I supposed to move into the middle lane when approaching cars entering the motorway from a slip road? If so, what's the line between this and hogging the middle lane?

Yes you move to lane 2 then back to lane 1 when it's safe to do so.

If you can and it's safe to do so, it can be a nice courtesy as long as you move back over as soon as practicable.

We have a couple of local sliproads which are too short to get up to 70 and people always move across to allow traffic to join.

Middle lane hogging is just that. Being in the middle lane for no reason.

Thanks!

If you can then it's a nice thing to do. But as will be pointed out shortly no doubt it's the responsibility of the joiner to join the motorway safely.

And don't expect lorries to do it. Even though one did it for me this very morning.

Yes, I do as the joiners are generally going slower, I move back once past it.

In theory you shouldn't need to because traffic joining the motorway is supposed to give way to you - the dotted line between the slip road and the motorway us actually "give way" markings.
In practice because the miners don't give way then you should move across to the middle lane if it is safe.

If it's safe to do so it's courteous. But not required. Don't slow the flow though (rhymes!). If you stay in the lane, don't change your speed.

"Joiners" not miners!!!

traffic joining the motorway is supposed to give way to you
The problem is that this is incredibly dangerous. If joining traffic has to stop or slow down when joining, there is no way that it will be able to accelerate fast enough to reach an appropriate motorway speed in time.

I had to stop once when I was first driving because they didn't move over, trying to get up to speed again was terrifying and I now hate joining motorways.

That sounds horrendous! I will move over where possible in future.