Dipper_Dave:
Although straddling before entry is best as chris says staying left and indicating right then left can also work well. Signalling to others your intent by a thumbs up or sweeping arm motion can also rescue a potentially aborted turn.
Your surroundings will give clues as to what junctions are like except London where there mostly a tad on the tight side.
In the end slow it right down pay careful attention to your mirrors (especially nearside) and fudge her round. More room can be gained from exaggerating the turn but be careful of approaching traffic, give way to them until one leaves you room to get in.
If your sure you need to straddle be committed and ensure nothing’s sneaking up your inside, slow it down and youl be amazed how making a connection with other roadusers can turn a potential drama into a non event.
Course tail swing etc must also be considered that’s why they pay us the big bucks. 
Youl be surprised how often that tight turn ends up not being that tight at all by planning ahead.
Oh and don’t forget to thank everyone in sight, even that little old dear walking round the corner with the pushchair or that cyclist coming up your inside at speed, yep multiple hazards always appear when one is performing a tricky manouvre.
Thats pretty well text book.
Acknowledging anyone who makes a space or helps you in any way works wonders, similarly if you show others that you are competent and aware by correct signalling and positioning a good percentage will help you for that moment to make all our lives easier.
As for commanding the road, there is a fine line between taking the room you need and using the size and weight of the vehicle to intimidate others, if people think you are a bully you lose all cooperation, and become another one who adds to the public misconception that all lorry drivers are arses.
Keep an eye on the way other traffic moves around you, competent drivers in other vehicles stand out, bicycles motorbikes cars vans lorries buses, even switched on pedestrians, if you act professional round competent drivers by driving defensively without overusing road commanding techniques you will find life is much easier overall in your driving life, good drivers instinctively can feel other good drivers, allow other good drivers to help you make normal progress for everyone.
One typical example here on the open road, using dual carriageways with roundabouts that are too small as many are for safe two lane driving around unless at snail pace, keep an eye on other traffic as you approach, you might well find that a car or van that was approaching and would be have been alongside you on the roundabout is actually hanging back possibly straddling both lanes a 100 yards behind you, you’ll get the feel for this type of competent other driver as you go on, he’s allowing you to take the easy swift line so do so if there’s no other traffic and its safe to do so, that way he’s as rewarded as you are by not having to slow to the aforesaid snail pace.
That way you both go through the roundabout swiftly and the car/van driver can follow your line but faster and be overtaking you very quickly a few yards after that roundabout in a semi slingshot manouever.
Note, always give that driver a wave/flash and/or pip on the hooter as thanks.
You’ll find that acknowledging others who help you does work out well in your driving lives, it’s a pity so many lorry drivers seem to lack any basic manners and courtesy these days, i suggest they are the ones who have to resort to bullying which trust me doesn’t work well in the long run.
