Unfortunately I have discovered that a previously accepted solution does not actually solve my problem.
The issue is the word "clone"
And a further unstated requirement is "Dynamic"
My attempts at a solution involved "select * into TableClone from TableOriginal"
followed by "update TableClone set ident-id = ident-id + 200000"
The big problem I have just discovered is that "select into" does not copy keys and defaults ie it is not a "clone"
so I really seem to have 2 problems
1) how do I dynamically clone any given table?
2) how can I drop the Identity constraint, update the erstwhile identity column & then reseed it?