What are the pro's and con's of S Plan vs Y Plan heating arrangements?
I am getting a new heating system and I don't know which one to go

S-Plan every time. Y-Plan is a dinosaur.

S-Plan is fundamentally more extensible (can handle more than 2 zones),
easier to understand and more compatible with modern equipment. Only
disadvantages are very slightly greater cost for a 2 zone system and need
for slightly more room for the extra valve.

Christian.