Aiden - in order to decide whether your line needs an overall CE mark as opposed to just ensuring the individual components comply with the relevant Machinery Directive (and note that second hand machinery doesn't have to comply retrospectively, only with the legislation that was in place when it was first used in the EEA / EC) you need to consider if it fits the definition of "assembly of machinery"
The Guidance to the Directive (link below) says:
"The definition of assemblies of machinery indicates that assemblies are arranged and
controlled so that they function as an integral whole in order to achieve the same end.
For a group of units of machinery or partly completed machinery to be considered as
an assembly of machinery, all of these criteria must be fulfilled:
− the constituent units are assembled together in order to carry out a common
function, for example, the production of a given product;
− the constituent units are functionally linked in such a way that the operation of
each unit directly affects the operation of other units or of the assembly as a
whole, so that a risk assessment is necessary for the whole assembly;
− the constituent units have a common control system.
A group of machines that are connected to each other but where each machine
functions independently of the others is not considered as an assembly of machinery
in the above sense."
Have a look at Articles 38, 39, 79 in this document
http://ec.europa.eu/ente...-42-ec-2nd-201006_en.pdf for more details.
Only you can decide if your line fits the definition. However even if it does you can carry out the conformity assessment and CE marking yourself and it only has to cover the additional risks that are presented by putting the individual machines together, not all the individual risks presented by each component, provided that you have the manufacturers' information on those machines.
The most important thing of course is that your line is in fact safe regardless of documentation and CE marks.