SEVERAL companies looking for a new Dublin headquarters are in negotiation for the next phase of the Sweepstakes office development opposite the RDS in Ballsbridge, Dublin 4. G & T Crampton is to start construction work in January on the 60,000-square-foot block, which is due for fitting out by the end of 1998. Palmer McCormack is quoting a rent of £20 per square foot for the block, which will have about 70 car-parking spaces. The new block will be built in the same style as the adjoining one occupied by Eagle Star since 1992. Roy Strudwicke's company, Ryde Developments, has planning permission for a third block of 60,000 square feet on the Ballsbridge site.