I use a similar setup, with a Windows desktop PC and a MacBook Pro. My photos are on an external drive connected to the Windows machine, and I sync the catalog and smart previews using Dropbox.
See see my post A Portable Lightroom Catalog on TipSquirrel.
Also, see my post on Using Lightroom with Two Computers.
MIchael that's perfect response solves my concerns completely.
I Presume I can then do something similar using my NAS drive which has its own "cloud" storage therefore not relying on drop box ?
Could I import historical photoshop library to LR and do the same ?
As long as both computers can access you NAS cloud storage, you could use it instead of Dropbox. Just remember always to allow the catalog to sync fully on both machines before launching on the other platform. Otherwise, you'll have conflicts.
You also asked, "Could I import historical photoshop library to LR and do the same ?" but I'm afraid I don't understand the question.
MMichael when I switched camera about three years back I also started to use raw. I then invested in LR prior to that all work was carried out in PSE I therefore have two catalogues one for LR and one for PSE however I might want to search use and edit a PSE picture when away from home ?