Well the problem is solved!

Tried Defenderzook's idea of putting pistons in the freezer ... sorry it didn't work and I was worried about the condensation

so borrowed the wife's car after driving her to work and a 70km round trip to the brake specialist in town ... He was no help ..had no idea why one side should go in and not the other.

Come home pull apart the calipers again and get out the calipers of the measuring kind and guess what?? one seal in each kit Britpart kit corresponding to STC1270 (the correct kit) was wider by .25mm, making .5mm in total.

pull out genuine LR kits from the spares box and bingo pistons slide in problem solved.

while in town I went to an engineering works and had the make up a gadget to help fit the seals.. I'll trial it in the morning