Is there any reason why you want to trade a fiat pair though? I don't recall any crypto exchange that focuses on fiat trading pairs, except maybe in the forms of stable coins like USDC-EUR, etc. I assume you only have GBP to deposit but the exchange doesn't provide a trading pair for that? Can't really give you any meaningful suggestions without knowing what exchange you use, as mentioned above. At the very least, you can do P2P to trade your fiat if you can't move to another exchange. CMIIW.