Our member Judy Barker spotted this piece on the Graham Rice blog, he has reached out for help with Euphorbias, you can read his request and provide feedback in the comments on his web page at this address:
Summary below:
Hello everyone, I need your help. I’m working on an article about variegated forms of the Mediterranean spurge, Euphorbia characias, as well as variegated varieties of the related Euphorbia amygdaloides and the hybrid between the two, Euphorbia x martini.
They can look very dramatic, but many gardeners have trouble keeping them for more than a year or two. So I’d appreciate it if you share your experiences. Which variegated varieties have you grown? Did they thrive or sulk? What conditions produced plants that grew well from year to year? Open ground, or containers? Which varieties did well, and which failed?
The varieties I have in mind include: ‘Ascot Rainbow’, ‘Burrow Silver’ (aka ‘Benger’s Silver’, ‘Silver Sunbeam’, ‘Honiton Lace’), ‘Emmer Green’, ‘Frosted Flame’, ‘Glacier Blue’, Helena’s Blush (‘Inneuphhel’), ‘Kestrel’ (above, click [on his site] to enlarge), ‘Silver Shadow’, Silver Swan (‘Wilcott’), ‘Tasmanian Tiger’, ‘Vanilla Swirl’ and ‘Variegata’.
Please add your thoughts in the comment box [on his web page above] or, if you’d prefer, email me your thoughts [the link is on his page above for the email address]
Many thanks, in advance, for your help. The piece will be published in the RHS magazine The Plantsman in December. I’ll be sure to let you know when it’s available.
Hardy Plant Society Hertfordshire Group 
I have grown Silver Swan. I bought 3 plants. It did really well for 3 years, and had made a good clump. Then it just did not get going at all in the spring. I put it down to the fact that we had very hard frosts etc. I did not replace it. I currently have Ascots rainbow, planted about 18 months ago,seduced by the colours in the leaves and stems.It is in a different part of the garden.It looked dreadful in April/may. I have a very cold garden, and had done nothing in particular to protect it, but it has come good thus far. Is there a hypothesis that thriving has nothing to do with the cold?
Perhaps you could put this reply onto Graham’s site too? Bill