The 30mph down the slip road incident, I agree could be partly your fault; of course the other driver should have gone faster but you should have adjusted your speed much earlier on the slip road so that there was enough of a gap between you and the other car to enable you to accelerate to match the speed of the traffic on the motorway once the other car had joined. This might mean slowing right down before speeding up again if you’re too close to the car in front (ie you’re speeding up, but they aren’t), but this is safer than just continuing, and expecting the car in front to speed up, getting too close to it, and then trying to join the same small gap at the same time, at a lower speed than the speed of the traffic already in that lane.
The lorry does not have to move over to accommodate you - most will if safe to do so (lorry drivers are usually more willing to do this than car drivers) but it is really up to you to find a gap. When on the mororway and approaching a slip road, a good driver will be looking out for traffic wanting to join and be preparing to move over, checking mirrors for the position and speed of other traffic etc; a crap driver just sits in the lane oblivious to the slip road - sadly there are more crap drivers than good ones out there so you have to assume the traffic will not move for you. Also was the lorry a left-hand drive one? - if so, see below - the driver may not have known if there was anything in the next lane so didn’t move over in case he side-swiped a vehicle that he didn’t know was there.
The second incident you mention sounds like it’s more your fault/due to ignorance - you say ‘maybe’ the driver of a foreign vehicle couldn’t see you? - it’s very likely he definitely couldn’t see you! There is a blind spot which means drivers of left-hand lorries cannot see vehicles running alongside them. So, when passing a left-hand drive lorry, you need to be aware that the driver will have no idea you are there.
As you approach a lorry (any lorry), you should be looking out for the number plates (are they foreign, so is it likely to be left-hand drive?); can you see the driver in the lorry’s wing-mirror? (if not, the driver also cannot see you); what traffic is in front of the lorry (is the lorry likely to need to pull out imminently?).
You should not begin overtaking until you can quickly get past the lorry in one move - ie you should never run alongside it, so you should ease off if necessary (gradually - maybe just touching your brakes to put your brake lights on to warn the vehicle behind, if that vehicle is too close to you), to allow a large enough gap to open up between you and the vehicle in front before starting to overtake (you’ll still likely get some arse behind you who can’t work out why you’ve slowed though and will try to ‘push’ you along, but ignore them!). Once the gap is there and you’ve checked the road ahead (to check the lorry isn’t about to pull out), you accelerate and overtake the lorry as quickly as possible.