You both have mentioned, but conveniently ignored, the fact that intra-UK bank transfers are free (ignoring ML restrictions etc).
If you compare the UK banking system to that of say, Norway (I think it is) where you have to pay around 6.00 just for the right to have a bank account you will see that UK consumers have a reasonable deal in this regard. The reason that it takes three days for standard transfers to be effected is that the overnight interest generated by the funds in transit effectively pays for the BACS system. Given that there is no eurozone equivalent, the banks charge for remitting monies to eurozone accounts.
We are lucky to have a banking system that permits free banking in the first place - the banks may make other, (and possibly unreasonable!) charges, but basic account management is essentially a loss-leader.
If we enter Eurozone it will be interesting to see what actually happens - I see no reason for the banks to suddenly decide to stop or reduce their charging structure as the costs borne are virtually identical - the only difference is that it would no longer be necessary to convert the funds into euros. Hence treasury costs are reduced, but the remitting costs remain the same. We will see!
MC