Pipe extensions for new rads

[Hillabaloo]

I am replacing two radiators. The new radiators will be larger and I will need to change the pipework.

The existing 8mm microbore comes out horizontally from block walls (the floors are solid). I will need to extend at least one pipe to accomodate the new rad. Basically my question is what options do I have? I attach a diagram that I hope shows what I want to do with one of the rads.

Thanks in advance.