Oh well, a simple internet search states that you probably cannot do that.
We only support transfers in local currency. So, if you have a PayPal account in England (GBP), but want to transfer money to your bank account in Germany (EUR), you may be subject to cross border conversion fees.
You best bet is to use TransferWise to withdraw from PayPal in USD to a USD Wise (TransferWise) account, then use their much better rates than PayPal to convert to GBP and withdraw to Monzo.
If someone else would like to correct me, I’m all for it.