Please, don’t buy MK as a one-off very special bag. They are everywhere at the moment, which really cheapens a brand - You can’t walk ten steps without seeing ten girls using them as school bags, for example. They look fake even when they’re not, (things like the crooked logo, for example), and a lot of people find them quite cheap and tacky looking (not that that necessarily matters).
Have you checked the Outnet? Bit of a random selection but you can pick up some really good bargains, and there is a wide range of brands. I’m sure I’ve seen lots of Coach bags on there.
Russell & Bromley also do lovely, good quality bags. I haven’t looked at their current range, but it’s probably worth having a look.
Oxblood is a great colour and goes well with pretty much everything. If i had to pick out of those two colours I’d definiteky go with oxblood/burgundy - IMO it’s a little more interesting than navy, and more versatile.
Good luck with finding your perfect bag!