AusBonsai

I have an opportunity to collect 2-3 Cotoneasters and 2 Small leaves Privets. All are around two meters in height and trunk diameter is 3-4cm with reasonable nebari. Can anybody give me some advice on how and when to collect for best survival
Thank you
Nilushi

late winter, early spring is what i would do. maybe these will be fine in autumn too.

Both species should transplant quite easily. You can cut roots back really hard - remember you will want to get it into a bonsai pot eventually so it is better to cut roots back harder when you first dig the tree and cut the top back than to restablish the tree, grow new branches and feeder roots and then find you need to cut the roots further and loose all the nice new root tips!
By all means collect trees for the practice but I find that very few make really good trees in the end - often taking longer to produce a reasonable tree than it would take to grow a better one from scratch so consider the possibilities carefully before wasting time and space on poor specimens. I have afew collected trees that i'm considering getting rid of because they haven't produced really great trees. It's just that a couple are amongst my longest surviving bonsai and have sentimental attachment.
If I have the option I prefer to transplant trees during winter when they are dormant but with weeds like those 2 species it could be possible at any time of the year. Last winter I collected a couple of olives and a privet from this area and got some more olives from a friend in SA. All are shooting well although some of the olives were a little slow to shoot. I've also been having a second look at the feral plums and hawthorns around here with an eye to possibly digging a few this winter - the problem is where will I keep them?

You can collect privet pretty well most times of the year with high summer and high winter not optional. It comes down to after care. If you are avid in your care so that the newly collected trees keep roots moist during the upheaval and get plenty of water and shade/dappled sun during the early days you should expect good results. I've collected privets in December and no problems. Too often we get trees when we have the chance as we might only pass that way once... so it comes down to really good after care.

i posted a subject exactly the same cotoneasters and privets
well i collected mine last year in winter PRIVET CANT DIE i was pretty new to the whole collecting plants and didnt take much roots with it , however not one died that says something i hope that helps