Hey,
here is the reply that GainCapital sent to me about this (I was seeing 15-20 pip spreads a few hours ago but now they are back to 4-5 pip spreads):
The information you saw on the website is actually correct. This phenomenon is exclusive to Sunday nights, when the market is extremely illiquid and the only banks open are in Australia.
The spreads tighten to our normal 4 to 5 pip spread within the hour or so, and thus, by 6:30, the normal spreads show on both the live and the
demo platform.