Real basic question :- I have been searching on the FAA site for some
mention of annual flying hours limits for commercial flying and not found a result. In the UK / Europe I believe it is 900hrs, so many per month etc.etc - is there an US equivalent, and where can I find the details ?

Thanks.

It all depends on your operation!!!
Like part 91, 121, or part 135.

Sorry - I`m thinking of scheduled Part 121 operations.

There's a bit more to this but the quick answer is:
30 hrs in a week, 100 in a month, 1000 in a year.

FAR Part 121 (121.471, 121.481, 121.483, 121.485...)

-T-

Or you can look up the FAR/AIM online and find the accurate info there.