There are a lot of misconceptions here.
1 - all of them sell plain black coffee
2 - a small plain black coffee is like £1, milk is on the side which you can top up. Only the drinks that is frothed up with syrup which a lot of people hate are £3. It's probably the same people who complains why coffee is so complicated in there, well, it's like £1 for a simple coffee, the option is there if you want it.
3 - get it to go, no need to talk to the hipsters, that is not required, in Coffee shops or in life.
They are a treat anyway, you can't and shouldn't drink like 5 or 6 a day if you are getting the fraps or getting those mocha, it's like 300 calories a cup! 5 of those a day you are pretty much done on all your calories unless you want to put on lots of weight. That's besides that it will cost you a small fortune.
So treat them like a treat, once in a while, stick to plain coffee, for the coffee. Get the filter stuff, then it won't taste burnt.