Scott,

A question first: Is this machine earning its keep today, and if so, how long a downtime can you afford? While I think there are enough people on this forum to advise you on this project, its not going to be a 1-2-3 and you're done job. I am not aware of anyone who does this sort of thing as a full time job, so it might be a little harder to find someone who can provide a one-stop service. (is there a demand for such? A question for all to discuss... but not on this thread!)

There is a level of research to be done, and possibly some machine specific coding/configuration. Like Robin I agree having your own in-depth understanding is the only way to stem the 'manufacturers drain on the bank', and having it fully and accurately documented means you can always hire someone to change it in the future, especially if you stick to opensource and common spec parts, e.g. making sure, for example, that the servo drivers you eventually buy conform to certain standards such as signal levels. Fortunately many of those standards are in place these days whereas in the past everyone had their own (again the manufacturers revenue generating 'lock in').

Oh, another question - where exactly are you in 'south east UK'?