I spoke to Catherine Hickman of Oxford Save Our Services who told me that she was personally completely opposed to the public sector cuts, including those that take valuable services away from the young and vulnerable. Of the government's utterly hypocritical rhetoric on the matter, she said "the government complain about the problems of teenage drinking and petty crime on the streets by disaffected youth on one hand, but then remove funding from the very services that offer them any form of alternative on the other."
By about 5.30, traffic was building on the High Street and people generally supported and cars beeping their horns in support. The protesters are chanting "We want what's fair, we want our youth groups here!" and "Save our youth centres: Why should young people pay?" and there is a generally good-natured atmosphere and a very minimal police presence so far.
The details are in the Guardian article.