you dont have to take it there. it just doesnt count towards your gpa if taken elsewhere (meaning it wont help/hurt you in trying to get departmental honors etc).
youre a freshman right? you seem to have most things planned, so i assume youre taking cell or maybe tested out of it, if so you can easily study abroad, even skipping out on sciences all together while in england. if you need to you can double up a semester with genetics and molecular (its tough, but doable, if you think thats an option only do it with Thien, doing that with Mullin would be suicide. Take orgo, physics, and bio all next year. im doing that now, its not bad. apply for the creative premedical scholars program if you like tulane's med school, then you wont have to worry at all.
if youre planning your schedules intelligently youll have no problem. youll only have to double up if you dont take any bios while abroad (i dont remember whats offered there). doubling up isnt so bad, you should be taking three math/science courses each semester right now, and by junior/senior year youll be done with math, physics, and chem so it wont be a change, plus later bio classes are pretty easy, it all just builds upon itself and makes even more sense the further along you go.
anyway, if you have any questions or whatever, ask here or pm me