Is there a limit on how much I can collect for currency CAD/USD/GBP/EUR in one transaction?

CAD: No, there is no limit.

USD: Yes. The maximum limit per transaction is $1 million ($1,000,000).

GBP: Yes. The maximum amount at per Faster Payments transaction is £1 million (£1,000,000).

EUR: No, there is no limit for Euro local collections.