When the flush of flowers is over chop off the foliage. This will result in regrowth of fresh foliage and reflowering.

Hello steragram, yes agree with scotsgran once flowering is over cut hard back i use shears for this task, and you will get a lovely cushion of foliage and more often than not you may get a second flush of flowers, could you move these to another part of the garden where they will benefit from more space and replace these with some dwarf varieties, geranium renardii would be nice, you could go for the blood geranium has lovely small purple flowers with small foliage and would do well by your steps, another one geranium Anne folkard nice pink flowers.

I think that most of the tallish ones do flop in the end. My clumps of geranium phaeum ( very deep purple or white ) seem to stay upright and Geranium magnificum makes a good medium height clump with big deep mauve flowers. They might be worth a look.

Agree with Julien and Scotsgran - when they've flopped outwards, you can usually see tiny new growth in the centre, and that's when you hack back to the middle, taking it all off and just leaving the middle, new growth.

Thank you everybody!
I have indeed hacked off the old growth now its more or less stopped flowering, and there is a lovely tall green clump in the middle. But that doesn't solve the problem of the flopping over too wide an area for the space alowed them.
Bsmboo, are you suggesting I hack off the flowering stems as soon as they flop, while they still have heaps of flowers on? am I hard hearted enough to be able to do it?
Surely that must leave you ages with no flowers while waiting for the second flush? I do love them and they look gorgeous but I was hoping somebody would know of one that didn't flop so I could move these somewhere else. It needs to be at least a foot tall, preferably 18" but stay standing upright. Am I asking too much of geraniums and if so can you think of anything else that would flower so long and look so lovely (and not pink - blue's what's needed just there)
Inverglen, I will have a look at magnificum.

Inverglen, Magnificum is well named and might do the trick.
Julien, the dwarf ones you suggest are lovely but not tall enough for where I want them because the steps are above soil level at that point.

To answer you, Steragram, no of course I wasn't suggesting that! I'd go with the G. magnificum, probably the most likely to remain reasonably upright, but in general, they are quite sprawly plants really.

Well - Inverglen has now kindly offered me two young ones to try - this is a great site!

And they arrived this lunch time now all nicely potted up and watered. Corncockle seeds in return on their way.