Hi
I had the exact same problem when my daughter was younger. My LO loved her sleep and fitted well into EASY, but going out was a nightmare, even though we did very short trips she would not go to sleep when we came back and just scream the house down. I tried when it was sleep time then A time,but nothin seemed to work at the time. I decided that going out after her sleep and feed was best. I started slowly only going out maybe twice a week, then gradual built it up. It was bad to start with as she wouldnt sleep when we were back in the house, but over time she got used to it and will now generally have a nap when we get in. She has even started to sleep abit when we are out (which she never did). Mt LO was a textbook/Angel baby - although she didnt feel like it at these times!
It did take time, and sometimes I dreaded going out, but it is so much better now, infact she gets bored just staying in and I am finding it hard to know what do do with her now ( shes 21 weeks)
I would say just perservere, it will be tough to start with, but it does get better.
Good luck