I bathed them in the kitchen sink till they started climbing out. Baby bath a faff.
Changing bag: boots do clear wash bags in packs of 3. The middle size fits several nappies, a packet of wipes, some nappy bags, a tube of bum cream and a disposable mat. I use the small one for my keys, purse etc and keep the big one at home to use for other stuff. The 2 smaller ones go in a big handbag or small back pack. Bottles etc went in a zip lock bag and I didn't really carry spare clothes. It's possible to travel light!
Bibs: depends on your baby. Ds1 was a dribbler and a bit sicky. I had some lovely velour bibs with a synthetic waterproof back by a brand called "mum2mum", and also got through a lot of muslins. Ds2 quite the opposite and we only needed bins for weaning.
Changing mat: I like the thick padded ones, around £7 from Mothercare. The provide some cushioning on a hard surface and don't roll up when the baby starts moving.