Megalytic pulls currency from source systems. For example, if the currency being used in AdWords is GBP, then that is what you will see in Megalytic.
The same is true for Google Analytics. Google Analytics sets currency to USD by default. So, if you need another currency, you will need to update your Google Analytics view settings.
Once you have updated your currency in Google Analytics, you can force Megalytic to synchronize and pull in the correct currency, as described here: Synchronizing Google Analytics Account Data with Megalytic.