The best and fastest thing to warm a bottle in I have found is the styrofoam cups they have at Asda's cafe. It holds heat better than a glass or warming container. I would put a cold bottle in and pur boiling water around, let it stay for a min or two and ta-dah a nice warm milk.
When we go out, I fill one of dd's bottles with 8 ozs. hot boiled water, another with cool boiled water. By the time she needs it, it is warm for her to drink. Then I just add the formulae. I carry a jar of formaulae that has about 4 feeds (8ozs) in it.
If it is nearly time for her to have a feed and we are going out, we take one ready for her to drink.
I don't think you should be too bothered about having the milk always warm, because they do tend to not drink the milk in on ego at times, if they are thirsty, they will drink the room temp. milk.
I tend to not carry a handbag or baby bag but instead a nice black knapsack, the more comparments the better. Not one of those the kids use for school. More like a trendy messenger type. I put changing mat and nappies one section, wet wipes in one of those tupperware type containers, cotton buds, cotton wool for emergency facial cleaning in a ziplock bag, hand lotion, bonjela, gripe water, lip balm in another, and the bottles and formulae in the largest section. My chequebooks and filofax fits into another section. That is all I need for baby and me.
I found some brilliant plastic containers that fits neatly under her cot. About 24 x 14 by 7 ins high, and those hold nappies, extra car seat covers and those welcome packs and stuff you come home with or tend to get in the post. Nice and compact.
I have made several fitted sheets that coordinate with our bed linens and change them as often as they get dirty. The mattress can be wipe cleaned, so that is a bonus. Flannel and all cotton sheets works well for us.
The above probably doesn't help but it does work and I hate carrying loads of stuff and seeing stuff all over the place.