If you want more plants, propagation is usually by cuttings or layering. Or has it got a bit out of hand, more woody than you would like? In which case pruning might help to regenerate the plant - but you'll need to know which heather you have as that will determine when to prune and by how much.

Urbanite is quite correct on the best way to propagate heathers but to answere your question; no, tou can't split heathers because they just grow on one stem.