I'm not a fan of diamond cut and the Austins were the one thing that I didn't like when looking at the car. Also the offset on the Austins leaves quite a large gap inside the arch, I initially looked at Prets but was put off due to the reports of them cracking and also the used prices were high. Settled on 18" BBS CH-Rs and have not regretted the decision at all, they look better while much better filling the width of the arch. My insurance company don't charge me any more than the standard wheels (some of the other mods are another story!).
I seem to recall that I managed to get around £500 for my old Austins, although they were in better condition that what you are describing with yours... but the important thing is that it's less money to convince your Mrs to spend if you get rid of the old ones ;-)