If they are RS1600i tie bars fronts then no.

But the rears will.

To be honest im struggling to understand exactly what bits you have.

The S1 has big cast corner plates up front with a side bolted bush.

The RSi has an aluminium crossmember with a front mounted bush.

If however they are TCA's then they should fit but your castor will be wrong.

The early XR3 (or Mk3 Escort) was a strange affair with strut tops in a different position to most later ones, this seriously affected camber on the front wheels and was corrected shortly after. Most of the bits will fit but it leaves your struts at a angle that was not as factory set. Shouldn't really affect much if the bushes at the top of the strut are fresh.