I tried them on and walked in them and they are more than a half size small. If you normally take a size 8 US, you should order the size 8 UK (9US). These are double plastic warm winter "hikers", step in crampon compatible. They may be a little more than what some would deem as required in winter Whites, but I am getting them for just that and the Adirondacks. I plan on winter hiking, snowshoeing, cramponing, in them all day and then again the next. I also don't plan on covering 20 miles a day in them, however.
I don't believe these would be recommended for vertical ice use by experienced climbers as the ankle is not able to be really locked down tight, but I don't do vertical ice.
"For vertical and mixed ice climbers, the new Scarpa Alpha is designed to be the most lightweight, precise, comfortable plastic boot made. This comfort and precision is due in part to the fact that the Alpha is created on an asymmetrical leather boot last. A lightweight thermoplastic carbon fiber midsole provides rigidity and a low profile rubber sole places your foot closer to the terrain for ultimate sensitivity. The tongue and ankle areas of the shell are made of softer Pebax for climbing and walking comfort and to provide a soft forward flex. The ultimate plastic boot for performance, comfort, warmth. Designed to enhance mobility and enable precise foot placements. Speed lacing system provides quick, powerful closure."