The trouble with Mulberry, and a lot of other designer brands, is that a large chunk of the money you are paying is for 'exclusivity' or 'status'. Mulberry is the classic example here, because they used to be much cheaper. At some point, they got a new CEO who decided that in order to increase the brands 'exclusivity', they would hike the price. In other words, the extra money you are paying is Mulberry's attempt to price out the riff raff and make their more affluent buyers feel superior, rather than for any increase in quality. They are status symbols, which is why many people see them as tacky.
You need to think about why you are looking specifically for a £1000 bag. If it is high quality you are after, and you want your money to go on quality, then I would look for something niche outside of these mainstream brands. If you particularly like the design of the mulberry or other designer brand, and think it's worth paying the extra, then go for it, but it doesn't sound as though you do, otherwise you would already know what you wanted and wouldn't be asking people online.