Hi Kezza,
Cherry trees are normally quite shallow rooted but can be extensive. Rowan on the other hand are usually deeper.
If you intend to dig them out by hand, you may find it much easier if you cut the tree to about 3ft from the ground to give some leaverage as you excavate around the roots.
Another option may be to hire a stumpgrinder and opperator to do the job for you.
You can also buy products such as 'Rootout' or 'Deeproot' which will stop the stumps from resprouting and rot down faster, but obviously this method willl take much longer.
Good Luck. Tbird+