Do you think this wall could be repaired or a section rebuilt? 
The  tree roots have affected it quite significantly. Obviously the tree will be removed. 
Any suggestions or ideas welcome. Thanks. 

You can definitely replace a section, but no matter how good a bricklayer you find it will always look like a new panel. 
even if you find the exact brick match the original wall would have aged over time. 
 

depends if you can stand seeing a different colour section or if you have the funds to replace the lot. 

Thanks for the reply.  Do you think brick cleaning would help to make it look less obvious? 

1 hour ago, Jothetaxi said:

Thanks for the reply.  Do you think brick cleaning would help to make it look less obvious? 

Yes, and re, pointing the original section at the same time the new section is pointed would at least get the pointing to match. 
 

when you remove a tree the demand for water is removed and clay may expand again. 

so bear that in mind.  it is going to move again.

Thanks for the replies. Really helpful.