UCAS applicants get top priority as its regarded higher than direct applications but you can still apply directly.
Its like UCAS is FedEx and direct application is Royal Mail.
Basically go through UCAS as it saves hastle and time and gets you in 1st.

As for dates, if you get em in early you application gets like a 5 min overveiw and they decide, if its in around feb time then it gets 30 secs and is just plonked in the "no" pile so get them in early.

Rubbish! Of course it makes it easier to get it in earlier but I know plenty of people who left it extremely late, it's a paradox that you have to do it early. Most unis do not accept direct applicants.