It really depends on your existing setup. I decided to separate zones when I had to get a new boiler. It turned out that the existing plumbing supported zoning - I had valves in the hot press that I could manually turn off for example if I wanted radiators all off but continue to heat water.
The plumber was able to replace these with motorised valves. There was a lot of cables to run, but it didn't need additional plumbing work, or ripping up floorboards.