Thanks very much, Pieman!

Latest update: it's been just over 4 weeks since first injection and just had 2nd injection 2 days ago.
I think I can say with some degree of certainty that there has been improvement!

Definitely less red overall, some areas still redder than others, but turning to a shade of pink in many places. Definitely less scaling and shedding, flakes being shed are much smaller and finer. Itching is also significantly reduced, although it is still there. Pain associated with dryness, cracking, etc. has almost entirely gone (actually it had already begun to lessen in week 3), which makes a huge difference! There are some small areas that have begun to flatten out and are almost smooth, but still rough in most affected areas. Patches are still well-defined. No complete clearance in any areas yet.
Annoyingly though, the places where I want it to work the most, i.e. the most visible places - the face, neck and hands, are being the most stubborn and are still quite red with raised rough patches.

Definite improvement on the face, but still visibly pink.
I just hope now that the improvement will continue. Will see whether the 2nd shot has any effect in accelerating the change.
Stelara has already made a difference to how bearable it is, although for £10000 a year, I expect a lot more! I know, I'm not the one paying for it!

Next dose is not due now for another 12 weeks.