If you decide on Photoshop CC then you won't save any money trying to stay with your standalone version of Lightroom 5. Photoshop CC and Lightroom are offered together as a creative cloud package. There isn't a package that just offers Photoshop. So I'm not sure what you will accomplish by subscribing to Photoshop CC and then staying with your registered version of Lightroom. I don't know what complications you might run into. When I switched to the creative cloud subscription plan I replaced Lightroom 5 that I had been using. The programs are exactly the same. It's just a difference in licensing.
Photoshop CC has some nice features that you will not be able to get if you purchase Photoshop CS6. In the long run, it might seem that you will be saving money by purchasing standalone licenses. But eventually those versions will be obsolete, no longer supported by Adobe, and you will have no ability to update them other than to purchase upgrade versions. I decided it was easier to spend $10/month because I'm retired and it's easier to budget that amount than to come up with the money to purchase upgrades when they are needed. But that is something you will have to decide for yourself.
thanks Jim for the reply - have done as you advised and all seems good
all best for the New Year
Yes, I did initially have my pre-CC Lightroom running alongside Photoshop CC so I know it's possible. I have since un-installed the standalone Lightroom and now use the CC version on that PC. If you don't want Photoshop CC then indeed it's probably cheaper to stick with your already registered version of LR.
If you decide against CC, once the trial is over, you'll have to un-install the CC version of Lightroom and install the stand-alone one using your existing standalone LR licence number. You can't just add your existing licence to the CC version you're trialling. You won't lose anything you've done in any LR catalogs.