OK,if I was you I'd start with the basic's.Make sure the following is correct,

1.Tyre pressure,it's 26 psi all round on a standard RST
2.Are the tyres a good brand,in good condition and the same make on the back??
3.Are the shocks and bush's in good condition or have they done 90,000 miles??
4.Are all 4 wheels pointing in the right direction??Get the car checked on a 4 wheel alignment rig.
5.Have the Mondeo alloys got the correct off set for a RST???

"so what's been try'd and tested over the years to get thease old S2's to handle nice? "

To answer youre question,I always felt an RST on Koni top adjustables and lowered 25mm/30mm handled really well.I use Chassis Dynamic's springs.Got both from the Woodford garage in Devon.

Hope the above helps you out,regards Micky