Yes. You will only be charged the fees for the SWIFT transfer including any additional fees taken out from intermediate banks during the transfer. Depending on the amount to be transfered - let’s say £5,000 - these fees might be higher than the conversion fee at Transferwise.
From experience there are no fees for SWIFT USD transfers from to transferwise, and a single $3.30 from transferwise to
As an example, if I transfer $1000 the $3.30 transfer fee equates to .33 percent. This is about the same I have to pay for the conversion from USD to EUR at my local bank.