Here's some links to other sites which you may find useful:
Silverback RC Products Ltd have been designing and manufacturing aftermarket parts using the some of the toughest engineering grade polymers possible for the popular HPI Baja 5B, 5T, and 5SC models.
Innovative-RC are a manufacturer of many aftermarket parts for the HPI Baja. From Aftermarket chassis to Big-Bore shocks you will find it here. They also stock a wide range of engine spares and parts.
Bashing Groups & Clubs:
As the name suggests a group of guys in Ireland doing what Bajas do best.
Holding events all over the North-East of england.
A club with many daily events covering the North West.
Dedicated bunch of guys, check the link for meetup locations.
Organized bash days in the South-Coast area.
Daily events and track setup in North Yorkshire.
Group of guys in the East of England.