Currency account basics:
If you receive a payment in Euros to your via your personal EUR IBAN, then the monies received would remain in Euro.
There will be no currency exchange or conversion involved.
Exchange Rate Impact on Amount Received:
You can however, exchange (convert) the Euros received into the Pound Sterling.
If the pound strengthens, then the amount of GBP that you will receive after converting from EUR will decrease.
If the pound depreciates, then the amount of GBP that you will receive after converting from EUR will increase.
Worked examples:
£1:€1.1
£100 → €110
€11-0 → £100
£1:€1.2
£100 → €120
€120 → £120
€1:2:£1
€120 → £100
£100 → €120
€1.1:£1
€110 → £100
£100 → €110