While its larger theatrical cousin across town is readying itself for a refurbishment, the Headgate Theatre has been quietly going about its own.

Starting this weekend, the Chapel Street North venue will open its doors to volunteers, audience-members and arts groups, to reveal the extent of the £170,000 expansion.

It was 20 years ago the Theatre Arts Action Trust was formed as a charity to find a permanent home for the dozens of local theatre groups who wanted to rehearse and stage plays in the area.

Since opening its doors in 2002, the Headgate has steadily grown into one of Colchester's artistic treasures staging works as varied as Waiting for Godot to Tarzan the Musical.

In the last few weeks it has put on Platform Musical's the Pajama Game, a new show by Colchester composer Olly Medlicott, Rockstar, last week's excellent Playhouse Creatures and this week All My Sons from Colchester Theatre Group, pre-empting a West End revival with Sally Field and Bill Pullman.

David King, Headgate chair, says: "When the building next door came up it was just too good an opportunity to turn down. It meant dipping into the David Forder bequest, and more help from the wonderful Hervey Benham Trust, who helped us out when we first started, plus a whole host of fundraising and donations from our incredible volunteers and patrons."

Work started in earnest from January until the middle of March, all overseen by Headgate stage manager, Stephen Peeling, who project managed the whole operation, since which time a team of volunteers have been working hard to put the finishing touches to the new spaces.

Along with the main auditorium and dance studio above it, the Headgate now has a huge rehearsal studio space, available for local groups to hire as well providing a space for creative workshops as well as some unique performances.

Dawn King, who looks after the education in performing arts at the theatre, adds: "Education has been one of the theatre's key objectives and over the years we have provided a venue for Kids Acting and Theatre School (KATS) on Saturday mornings, Colchester Institute students, Stephanie Cook School of Dance, and Musical Theatre holiday workshops.

"We also host a schools creative writing and performing project, involving St Thomas More, North County and St John’s Green schools as well as writing workshops and the Act V drama group.

"Having this space means we can still do these and much more, especially when the Main House is in use at the same time."As well as the rehearsal studio, the Headgate has a new workshop space, storage rooms, entrance foyer with accessible toilets and changing facilities.

This Sunday the new theatre spaces will be opening up for volunteers, and those who are thinking about volunteering from 2.30pm to 4pm, while the official public launch is next Tuesday, April 16 at 3pm and 6pm. To register a place e-mail administrator@headgatetheatre.co.uk