Hi, firstly ignore the hand wringing/bench/how much brigade. Their posts are quite amusing though 
The Mulberry bayswater won't date if you get it in a classic colour. I have a bayswater but not in the oak. I agree with Amber. Have you thought about a Smythson? They are such beautiful bags. My favourite one is the Nancy, but the Agatha is gorgeous too. They are about the £800/£900 mark.
Balenciaga City has been a stable for a good few years now and is now considered a classic. The really roomy bag is approx £1200, however, I saw that they have started doing smaller versions for approx £800. They are gorgeous bags.
The Chloe Marcie is new and comes in a tan. Again the really roomy one is approx £1100 but they do a smaller version for £800 ish. I agree that it is a heavy bag!
If you are thinking classic tan, then you should also think about Longchamps or Tods. Classic with a bit of twist then maybe the Madison bag by Coach (its actually cheaper approx £500 ish from memory). Also Micahel Kors do some really gorgeous tan bags.
Prada bags tend to be well made and I always think of as classic (eg more so than Gucci). I think they date well so I still use Pradas from 10 years ago.
Finally, I would also recommend Aspinal. Not as well known as Mulberry and slightly cheaper. Check out the hepburn bag which is beautiful and I always get compliments when I use mine.
Hope that helps!