The GBP/USD pair bulls initially seemed unimpressed with surprisingly strong manufacturing data before the pair regained its bullish momentum and spiked to a fresh session high level of 1.4595, a whisker away from 1.4600 handle. The GBP/USD pair remains in spotlight because of its volatile moves on increasing uncertainty surrounding the EU referendum in the UK on June 23. An initial bout of selling pressure dragged the pair sharply lower to test 1.4500 handle before an impressive UK manufacturing and industrial production data assisted the pair to erase early losses.Uncertainly over the implication of 'Brexit' on the UK economy remains key fundamental overhang for the GBP/USD major. Hence, the pair might continue to react with extreme volatility to the outcomes of various polls until June 23, when Britons cast their vote on the critical EU referendum.Technical levels to watchOn the immediate upside, 1.4600 round figure mark remains immediate strong barrier, above which a fresh bout of buying interest could assist the pair back towards 1.4700-20 strong resistance area (nearing 200-day SMA near 1.4730 region).Meanwhile on the downside, 1.4500 round figure mark now seems to have emerged as immediate support. Failure to hold this immediate support could drag the pair immediately towards 1.4465-60 intermediate horizontal support before the pair heads back towards 1.4400 handle support. Weakness below 1.4400 handle might continue to find strong support around 100-day SMA near 1.4350 region.