Sure thing! Just follow the normal procedure to top up through UK bank account (take into account it’s not instant).
Then, when the funds are in your account, just click “Send” and select “To bank account”.
Add your recipient, choose the amount to be sent in EUR (or any other currency) and it will be automagically converted on the go. No need to convert it beforehand (the exchange rate will be shown when making the outgoing transaction)
The bank transfer top-up is free, foreign exchange is also free up to 6.000€ and SEPA transfers are either free (standard) or paid (turbo)
Hope it’s useful