Thanks for the reply, I think I may have mis stated what I did
The linked info is the start and finish date- so for task "X", I copied the start date of task a and pasted into task x start, then copied task b finish date and pasted into task x finish. Not an ideal solution, but it performed the function that was required- or at least, the one I was told was required!

I resorted to using a summary task with start dates for each resource as a direct ss link, and the same for finish, then hammocked these to give durations. That way at least I know where the info came from.