I bought the most amazing free standing antique pine kitchen from Around the Irish House. We designed 1/2 the kitchen with the owner, and bought the other pieces from the showrooms. It's solid wood and extremely well done. Very reasonable. Perfect after sales service (unique these days).
My mate got his freestanding units from Habitat and they are very attractive it must be said. But (and there has to be a "but") it is difficult to organise your services around the units- you really need to plan your wiring and plumbing carefully so as not to ruin the "freestanding look". The other downside that I can see is that cleaning under the units, around the feet etc could become a chore.
Agree with Carpenter. Have a new island unit myself with the hob on it and having issues trying to fit the island extractor (electrics, vent etc.). Have this well planned out before you go for it.