Bailey pipework freezing up

I purchased a Bailey Pegasus Verona  2 in September 2011 with the intention of using it touring at all times of the year . I have recently returned from a shake down winter tour of the UK to test Baileys much acclaimed  winter use capabilities in anticipation of using the van on the continent  in possibly more testing conditions .Despite  taking all the obvious precautions to eliminate any chance  of the  external water supply freezing up  I found on a number of occasions when the temperature dipped below freezing, the van internal  hot and cold water pipes froze resulting in no internal water supply . Even with the internal van ambient temperature at a constant 23deg c day and night the internal pipework still froze up including  when  using the on board water tank. Has anyone else experienced  similar problems with Bailey Alu-tec  vans ?