The police by stopping you pass out information are possibly acting against the Human Rights Act which allows freedom of speech. A goog compromise would have been to put away your table and then just hand out leaflets - the handing out of leaflets could in no-way be described as obstructing the highway without lawful excuse.

I got the following information from the Free Beagles website, which is a legal resource for animal-rights and other activists. I highly recommend it

Obstruction of the Highway:
Section 137 of the Highways Act 1980 makes it an offence to cause a wilful obstruction of the highway without lawful authority or excuse.

Points to Note
Many animal rights stalls and assemblies may well cause an obstruction, but the key point is whether or not there is a “lawful excuse”. It used to be the case that there could only be such a lawful excuse for obstructing the highway where you were using it for passage or re-passage or for ancillary matters – eg stopping to read a map. But more recent case decisions have interpreted the right to use the highway much more liberally, so as to include, for example, the handing out of leaflets or collecting for charity. Nowadays the courts are much more mindful of respect for ECHR convention rights.
So it is not necessarily the case that an animal rights stall or a picket outside a shop on the highway is causing an unlawful obstruction, as the police or council officials often maintain. Leading cases state that all the circumstances must be considered in determining whether the obstruction was unlawful, including the duration and the purpose of the obstruction. Now that the police are legally bound to respect your rights under the ECHR, so they have to interpret their powers so as to be consistent with those rights. And the courts must, wherever possible, interpret legislation so as to be consistent. This means that the police and courts cannot interpret the law so as to prevent your demo from taking place, as this would amount to a denial of your convention rights.
You cannot be arrested for obstruction where you are actually walking along the highway.
Although it is not strictly speaking an “arrestable offence”, you can be arrested for wilful obstruction of the highway under under Section 25 of PACE.