Are metric 28mm olives fine on imperial 1" copper?

[WaterTight]

And used with 28mm compression?
Thanks

 

[WaterTight]

Or whatever size it is, one up from 3/4"

 

[Best]

Yes. They are close enough & the old imperial 1" pipe is very fractionally wider, so that will mean the 28mm olive will be a nice tight fit.
One thing I should mention is you might find the modern brass nuts on the new fitting will be very tight in the 1" pipe. Especially cheap fittings. Conex are nice slack nuts

 

[WaterTight]

nice one cheers.