@okarin_niqqa first, it’s important to note the currency pair comparing the exchange rate between the US dollar and the British pound is always written as GBP/USD, never the other way around. If you believe the British pound will rise relative to the US dollar, then you can buy GBP/USD. If you believe the pound will fall relative to the dollar, then you can sell GBP/USD.
If you sell GBP/USD to open a trade, then you are in a short position. You are short GBP and long USD. In this scenario, you would indeed earn rollover interest, if you hold the position open through 5pm New York Time which marks the cutoff between the end of one 24 hour trading day and the start of the next in the global forex market.
The screenshot below is taken from the Current Rates window of our FOREXTrader platform. It shows you can earn 28 cents in rollover interest for holding a mini lot (10K) short position in GBP/USD today at 5pm. That’s about $2.80 for a standard lot (100K).