you just have to keep changing them over bud ever that or put a sock over them or wrap em in cotton wool... good luck
Even Wrapping them up in socks dont work, the tip just freezes so no water comes out. I find having two water bottles makes it easier and less hassle.
Royal were you based about?
i'm out now pal i live on the humber, there is a thread on here with all different tips to stop water freezing but the best thing is to just change them morning and night