phil 100 is a popular minor, so you will find that there will be about 250 students in the lectures (well, technically, quite a few people wont turn up lol)
the seminars are in groups of about 10/12 so they are much smaller.
in the 2nd/3rd year, when you get to chose your modules, the class size is much smaller, and the lecturer takes the seminars, so they get to know you too.
i felt i picked it up quite quickly, and you get feedback after every essay, so every 5 weeks. what is more, none of your 1st year results count towards your degree, so you have a year to get the hang of it. don't be disheartened by the results of your first essay, it is a completely new style of writing! (this goes for any uni)
adding to what affinity89 said, you take 3 courses in your first year, and you can pick any one of them up as your major in your 2nd/3rd year. so if you dont like phil or politics, but love your other part 1 subject, then you could change course to that.
finally (this is turnig into a long post, sorry)
i also applied to nottingham, what swayed me to lancs was the feel of the uni. i loved the college system and accomodation, and all the lectures seemed really open and easy to talk to.
if however you prefer notts, go there, i have friends from school who are there and they are happy. in my opinion they are both on equalish standing (maybe notts is slightly better, but i dont think it makes much difference....)
hope that helps =]