If you are the owner of a property, and found your property being occupied by squatters, you need to report to police immediately . You can not use violence against your squatters or threaten them.
To evict the squatters, you need to apply for an interim possession order (IPO) to get your property back, which usually can be obtained from the courts within a few days. (www.justice.gov.uk/guidance/courts-and-tribunals/courts/proc) The squatters must leave with 24 hours after receiving IPO, otherwise they will be arrested.
For detailed information, you can visit: www.direct.gov.uk/en/HomeAndCommunity/WhereYouLive/Derelictb