I disagree.
The attractiveness of AUK is its quirkiness, if the word exists... in a world of instant gratification, it is an oasis of peace... a spanky interface will attract some and will put off others. Bear in mind the average age of AUk is well over 50, trying the rejuvinate the organisation could backfire.
BCM is extremely popular, despite its archaic entry method and I can't help thinking that's part of the charm... you actually have to put some effrot to enter, effort to plan your own route... it makes it a bit special in a world of corporate organised entertainment.
A slightly nicer website could a good thing, a 340 k website seems an extravagant thing for an organisation that is largely based on frugality.
Moreover, as I said here and elsewhere, it's pointless trying to increase the customer base, if you don't increase the offer and I can't see the latter going up to be honest