The big moves are coming in just a few hours. This is a certainty regardless of the vote's outcome.

First off all, you should trade what you see and not what you think or what the results show. Traders make money on markets movements not poll results. The market is always right. So..beware of "buy the rumors, sell the facts".

The liquidity will be very thin, this means that a smaller sum of money can move the market greater than in normal conditions.

"Remain" vote has, right now, a much bigger chance than "leave" so the markets can price in this information way ahead of the official results.

Look at the price action of gold or S&P 500. These are risk barometers so their price action could signal a reversal on Gbp pairs.